Interview with Dr. Philip Anderson By Dr. Lillian Hoddeson July 13, 1987

Transcript

Hoddeson:

... notes...

Anderson:

—not very many. Four pages.

Hoddeson:

Four pages of notes.

Anderson:

Four or five. I just started putting down names, and realized it went on forever. Michael wants to be on the… Yes. What are the questions?

Hoddeson:

Well, I thought we could discuss what should go into an ideal magnetism chapter in the history of solid state physics. Imagine a chapter of about a hundred pages, with starting from an arbitrary point, and ending in the fifties and sixties. In the book, we were supposed to end every chapter at about ‘55, but it seems that all of them are moving into the sixties. There doesn’t seem to be a natural break point. For example —

Anderson:

That’s not a good break point. The war would have been a good break point after that. Not really natural.

Hoddeson:

There is no natural break point. Why is — wait a second — …Well, why is the war a good break point?

Anderson:

Everyone stopped work and started working on other things, more or less, and the other thing is that there was this tremendous technological thing which came with the war. The whole of spectroscopy essentially started after the war. Nothing before that.

Hoddeson:

Right. How would you organize it?

Anderson:

I don’t know how. Well, I suspect now there’s lots of material. I don’t know, I haven’t seen —

Hoddeson:

I haven’t it looked at it all either. There’s material on early French work. There’s some material on early Japanese work. I don’t know how well it’s going to be integrated into the chapter. There’s some material on neutron diffraction. Once again I don’t know how well that’s going to be integrated. There is material on van Vleck and Stoner and that —

Anderson:

— yes, and have they interviewed Charlie Katel (?)

Hoddeson:

I don’t know.

Anderson:

He was an absolutely key figure.

Hoddeson:

I know. Katel is a tough one to interview. He doesn’t like to be interviewed on account of his defect.

Anderson:

Oh yes, I suppose that’s true. But everything I say, Charlie could say, because he was really my — he wasn’t supposed to be, but he was really my mentor. At NFL. (?) (or Bell?)

Hoddeson:

Oh, was he?

Anderson:

I learned solid state physics from him. I didn’t learn anything from van Vleck because I was doing gas phase spectroscopy. And I learned a lot from Shockley, but then, there’s always the problem with Shockley competing with you all the time, trying to compete. So Charlie was really an influence of the first magnitude. And in the end, well, I didn’t even take van Vleck’s course. I audited it a little bit, and I got bored, left, although I took his course in — I don’t know why it wasn’t a good solid state course but it wasn’t.

Hoddeson:

When did you take it?

Anderson:

In ‘47 I guess. I listened to Gorter (?) and ? They were both guests during that period. Gorter of course is terrific. He just talked about his thing, paramagnetic relaxation. So he was in there, and communicating very much. Bloembergen of course came from Gorter, I suppose, or at least he came from that school. Well, I wonder, what would they be? The Mainlaws(?) were a big thing. I don’t know whether they’ve done anything about the Mainlaws.

Hoddeson:

I have to check that. I suspect that this chapter is just deficient. The last one that’s coming in, and —(crosstalk)

Anderson:

It’s really solid state physics. And I know what the old-fashioned magneticians were like. They were materials people. You put a little bit of nickel into some iron and … ? … was magnetism, and Charlie Katel got absolutely furious with them.

Hoddeson:

Why?

Anderson:

Because he would use people like Williams and Nesbitt, really good physicists, better physicists than Bozarth, and would use them to fill in spots in his phase diagrams. Ridiculous (?) etc. and all his calorie(?) systems. Whereas Williams was inventing the science and studying domain walls. I don’t remember what Nesbitt was doing at the time, but it was important. Williams in particular was a much better scientist than Bozarth.

Hoddeson:

Was Bell really the major center?

Anderson:

The major center for the physics.

Hoddeson:

The physics of magnetism.

Anderson:

Yes. There was Oxford. There was Bell. After Charlie went there, there was Berkeley. Otherwise I don’t think there was much of anything but Bell, except for the coherence spectroscopy bit, the magnetic resonance bit. And even that developed only after Charlie went to Berkeley, and a few other centers sprang up. MIT to some extent in the early days. Of course, the better magnet was developed at MIT, though I don’t know that they did much with it in spectroscopy. I don’t know, does the chapter go into paramagnetic resonance? And nuclear, NMR, is NMR a part of your?

Hoddeson:

NMR we’re supposed to be dealing with.

Anderson:

There’s so much history of NMR. So many complications, all that business of, oh, the relaxation problems, and the different kinds of resonance and so on. Charlie, I guess, when he came from MIT, who did he study with? I don’t know. Oh, Breit. Yes. Then he went to MIT as a post-doc. He really was very much influenced by van Vleck, but I don’t think he ever studied with van Vleck. He came to Bell and invented paramagnetic resonance with Yager, paramagnetic resonance. There also was an operation going on on studying domain (?) under Williams and Gait. That was important. The ferrites were invented of course at Phillips. That was a major center. I don’t know whether they’ve gotten Phillips.

Hoddeson:

I think they’ve done something with ferrites, at Phillips.

Anderson:

But then they didn’t do much physics of ferrites. They studied the paramagnetics and the structures and so on, but they didn’t do much with motions, …magnetic resonance. Now, later on, Clarkston and Walker (?) and so on. Then Blackwoods and Graham, and that sort of turns, he was the one who understood the spectroscopy and the line breadths and all that stuff. Very important.

Hoddeson:

By the way, I read your biographical memoir of van Vleck. Very good.

Anderson:

Well, you know, somehow people don’t emphasize his role in coherent spectroscopy. Well, neutrons. Of course, the first demonstration of –- Sholl(?) was very good. The rest of them were OK but Sholl was really the important one. And Sholl came to Bell Labs with the (crosstalk on tape) spectroscopy of ... and it was discussing with him that I realized these ideas about super-exchange were going to ... (crosstalk)... That stuff came from Charlie Katel too. Charlie was -– (?) and I were sitting together, for the first months that I stayed there. We arrived simultaneously. And Charlie came in one day and said, “What’s all this about (?) magnetism we hear about?” Next time we did something (other voices on tape ...) So Gregory started think about Eisen models, which was his thing, and I started thinking about other things, and Charlie I guess got me the old(?) paper on super-exchange. It wasn’t really, it was just an observation, it wasn’t a paper. And so I did a first paper on super-exchange.

Hoddeson:

When?

Anderson:

‘48, ‘49. And then Schow (?) came around, and we realized that it must be real, because it explained why the structure was the way it was, and didn’t have nearest neighbor interaction or (?) interaction. Then I did a couple more simple things in field theory, and I got my first invited paper out of it, so I would say it was Shockley who didn’t like any of this.

Hoddeson:

Why not?

Anderson:

Oh, because he had hired me to do ferroelectrics and I was damned well going to do ferroelectrics.

Hoddeson:

I see. He hired you?

Anderson:

Yes, he hired me. He was really the one who was hiring. (?) … cajoled or whatever. So, we then really began to take field theory seriously, and of course, — let’s see, I guess what happened was, I went to Japan and taught a course in magnetism over there. And there’s a Little Red Book exists on that course, where (?) knew much of it, but a lot of the people who later were Japanese magnetism people were there, ? and? and? and? — a whole gang of them. And then Bell Labs asked me to repeat the course, and they started this magnetism group back at Bell. So that was about your cut-off time. They taught? and? and also a number of people, Brubeck(?), the guys who discovered the double membranes were also in that course.

Hoddeson:

Did you spend a semester in Japan?

Anderson:

A little over a semester, yes.

Hoddeson:

A little over a semester. In Tokyo?

Anderson:

Yes. Cumbo. Now, Cumbo, we had two things in common. One was, we both did paramagnetics spin waves, and the paramagnetic spin wave paper was before that. Both of us talked about our early paramagnetic spin waves at a meeting that was reported in REVIEWS OF MODERN PHYSICS in ‘52. Very notorious meeting, because John Slater’s delightful personality was particularly evident at this point. We had a panel discussion in the evening, and just about the time that everyone else got interested, Slater got bored and said, “I think we have to go to bed,” and stamped off the stage.

Hoddeson:

Oh no.

Anderson:

Just before van Vleck was going to talk about his stuff.

Hoddeson:

He never did anything beyond what he did in the thirties, did he?

Anderson:

That’s right. Slater? Oh no, he tried to develop, and maybe even did develop a band series on SL magnetism. He did a band theory on SL magnetism.

Hoddeson:

Oh, did he? In the fifties?

Anderson:

In the late twenties.

Hoddeson:

The late twenties?

Anderson:

These things were, he didn’t write them up. He didn’t write them up. He didn’t like the insulators. He didn’t like the Pieirls idea of the strong interaction. And somehow, he wiped out of his — although he invented the Slater FMG(?) integrals, he wiped the integrals out of his consciousness, as not being what we now call U, a phase of magnetism physics. It didn’t fit band theory, so he scrubbed this out, is what he did. And therefore he couldn’t possibly produce an explanation for (?) being an insulator, unless it was anti-ferromagnetic, and he had this theory that it was anti-ferromagnetic (or paramagnetic?) and therefore it was an insulator, and got a band splitting on that. Slater would not have it that there was band splitting for any other reason than periodicity. And he just, although he’d invented much of many body theory, he just insisted on ignoring everything he’d done before the war.

He just changed. He had this dream of everything was going to be computed by the new computers, and nothing would be, nothing he did after the war — everything he did after the war was focused on that dream. And in the meantime, he came up on something which didn’t look like it was computable, and he just tried to wipe it off the map. So then Wax’s (?) theory of magnetism, and the Bott theory — later on, there was a spectacular incident that happened in ‘67, ‘68, very late. Even later. In the early seventies, there was a Gordon Conference. Slater gave one of the final talks. Jim Phillips very carefully asked him, what did he think of the VCS theory of superconductivity? And Slater said, “No computer can reach that level of accuracy at this time. Therefore, we have no idea whether or not VCS really is correct.” It was just so perfect, to show what his attitude was. This meeting was the first one where there was any kind of hearing for the van Vleck theory, or the (?) type theory of ferromagnetism, that later on became more or less the standard theory. And he just didn’t want to hear about it. I met Tuball(?) there, and we also had an interest in line (?) Tuball was picking up on these techniques which worked like, although we didn’t know it, fluctuation dissipation theory. He wrote a paper with (?) that was the next step on ideas on (crosstalk) exchange (?) and that went into the (?) theory, because it was Tuball who discovered the periodic boundary conditions. (crosstalk)

Hoddeson:

Why do you say Snyder invented the many body theory?

Anderson:

Well, he wrote the first theory of spin waves, didn’t he?

Hoddeson:

Well, simultaneously with Bloff.

Anderson:

The first theory, microscopic theory, you know, real theory in the sense of trying to deal with (crosstalk....) It was the predecessor of Herring and Katel. And some of the other stuff he did. He invented the SNGs, which was very clever. All these clever techniques for doing wave functions.

Hoddeson:

I guess so, I don’t think of him as a many body —

Anderson:

—no, he wasn’t really —-

Hoddeson:

Any more than I think of Heisenberg in the same way for his work that he did on —

Anderson:

— true. True.

Hoddeson:

— many electron systems.

Anderson:

Another person you may want to have some contact with is Herring.

Hoddeson:

Herring, I guess they must have — as I say, I haven’t really looked into this because it’s like.... What else do you have in your notes there?

Anderson:

Well, I was thinking about, unfortunately the notes are simply (crosstalk) — I should really be free associating. Well, after Charlie went to Berkeley, there was the initiation of cyclotron resonance. In the first place, all of the resonance work they did, magnetic resonance I guess at first was really Oxford. It was a game for Oxford and Leening. Leening was very important in that early stuff. We were competing. I know one thing, there was the Geemarker business, paramagnetic resonance. Charlie invented that just by looking at (?) Bernstein and discovering that they were organic magnetic compounds, and Alan Holden made it in our resonance group, measured it, and it’s ever since been used as Geemarker. I don’t know how important. They must be important in chemistry nowadays, although they weren’t then. They were a sideline in chemistry. We did a lot of paramagnetic resonance. We were very much hampered by our equipment, which was lousy. There was a Bitter magnet, that someone had made the wrong decision about power supply, and it fluttered to about 10 gauss, so we missed the first measurements of hyperfine structure (crosstalk)… (pause)… She seems to be a very highly reliable person.

Hoddeson:

Never thought —

Anderson:

Went to sleep. Had too much wine for lunch.

Hoddeson:

Didn’t see her at lunch.

Anderson:

Lots of interesting incidents, but then that’s not the stuff of history.

Hoddeson:

Well, it’s still good to get it on tape, some of it.

Anderson:

Yes. ... Early days of spinglass started in ‘44. When Charlie first went to — well, there’s a whole thing of diluted systems, of Charlie, I think basically Foster. Owen, John Owen from Oxford went to Berkeley, and he did some of these dilution studies on magnetic ions of metals, manganese and copper and so on, and then he went back to Oxford and did dilution studies on manganese and zinc oxide, which was important in measuring exchange integrals. We all were confused. It was a very strange set of data on manganese solutions in copper. I mean, some theory by, could it have been Condo? And there was some theory by Marshall. Marshall was the first one who pointed out the scaling laws. And the Mayo group took it up and developed this crazy Mayo cluster theory. And all of that happened I think before your cut-off date. None of the theories were anywhere near right. The measurements were more or less right. We picked it out as an interesting system to study.

Hoddeson:

When did the field of magnetism clearly, you know, become one of the central fields in solid state physics? For a long time, it was sort of off to the side. When did?

Anderson:

I think it was the (?) resonance techniques.

Hoddeson:

The resonance techniques?

Anderson:

And then for a long time, it really wasn’t a central field in solid state physics, it was a central tool of the resonance theorists. Fayer, your chapter doesn’t have Fayer in it, and it should, because Fayer was the inventor par excellence of resonance methods as a tool, double resonance and various kinds and so on. And the other name is Porter. Important studies, early studies of magnetic resonance. So magnetic resonance became a central subject. But it, you know, it never did, or it did for a while and then the focus —once we had cyclotron resonance and Fermi surface studies and so on, the focus suddenly became on Fermi surfaces, and magnetism went out again. It’s a central topic —

Hoddeson:

That’s an interesting pattern.

Anderson:

It’s a central topic of many body theory, for many years.

Hoddeson:

Yes. Right from the beginning.

Anderson:

Right from the beginning.

Hoddeson:

Right from the late twenties.

Anderson:

Right. From the late twenties. And a central topic of critical phenomena, because of the neutron. When Marshall and (?), once neutron diffraction rates became important, then Walter Marshall and the (?) group (crosstalk) tended to become central, very central to many body theory and solid state physics. Then the Brookhaven group. One subject that should be in there is chromium.

Hoddeson:

Chromium?

Anderson:

Yes. Well, you know, all the mistakes that the neutron diffraction made, it’s in my paper, that feeds this neutron diffraction, because of this big expensive — and had a lot of personnel in it — was believed, and again and again they were wrong. Chromium is an example of that. It’s the first metallic (crosstalk knocks out again…) There was a lot of work. In the first place, the neutron diffraction people declared it was not a ... (crosstalk) (pause) …Chromium, first they declared it wasn’t a neutron magnetic, and then they gave it the wrong structure. Then finally, with a great deal of pain, they developed the right structure. Magnetic transition rates were found by acoustic spectroscopy. There was Frank Moran, who studied all the transition metal oxides and found all these metal insulator transitions, which are not supposed to be Mott transitions but turned out to be, there not magnetic. (pause...)

Hoddeson:

I’m sorry, OK. Chromium was, anything else to say about it?

Anderson:

Chromium was, then there was — no, no, just, well, it’s an interesting case. It’s the first charged spin density rate. The first measurements were very early. Murray Kline who was at Bell Labs at that time, it must have been again in the late fifties.

Hoddeson:

The late fifties?

Anderson:

Or even early fifties. George Fayer came from the Berkeley group, came to Bell Labs, and I guess he was hired during the period I was in Japan, so he was already doing MNR and lovely magnetic resonance work on the silicons.

Hoddeson:

When were you in Japan?

Anderson:

‘53. He would have been doing that by ‘54, ‘55. That’s when they did the magnetic resonance work on the impurities in silicon, which eventually led to Endor and also led to the Schallow(?) impurity in silicon physics. It really was a part of the whole thing. During the period when semiconductors were the name of the game, magnetic resonance was the major technique or a major technique that people were doing real physics with, and so magnetism was very central at that time. Then, as I say, as soon as cyclotron resonance came along, and then the Fermi surface studies, it took a back seat, and one, electron physics began to be — the other thing was the development of optical techniques. Very soon, the semiconductor person was a person with an optical spectrometer, and measured conductivity, and that was about it. I can remember coming back into the field of amorphous semiconductors, being shocked to discover that nobody, nobody ever made a magnetic measurement of an amorphous semiconductor.

Hoddeson:

Really?

Anderson:

Because by that time, magnetism had dropped out of the bag of tools. And there’s also Pauling, you know. He always made a big fuss about magnetism as the criterion of one type, really thinking, you know, was it magnetic or what was the magnetic configuration of a given atom or a given RM and that told you how many of the electrons were in bonding.

Hoddeson:

Did he make any major contributions?

Anderson:

To magnetism? No. Except the wrong one, a very wrong one.

Hoddeson:

What was that?

Anderson:

The Pauling 1944 theory, he still believes in it, he still writes papers about it —

Hoddeson:

Oh, really?

Anderson:

He never believed in the theory of metals, you see. He believes only in resonating bonds. So he has a theory of metals along the lines of resonating bonds, and gives you a curve for the magnetic moment of the iron group of metals, which is what you would get a lot easier by just thinking about band theory a little bit. And he says this is an absolute proof of his theory of magnetism. And that was 1944. It never had any influence whatever in the field of magnetism as far as I know. It was never accepted by physicists. Herring, Herring’s key contribution there was that he put the field back together again.

Hoddeson:

How did he do that?

Anderson:

The van Vleck school, the old fashioned school always thought of magnetism as isolated moments moving around according to Wise’s theory and resonance was a phenomenon of individual magnetic moments, and there was the Stoner theory, the Stoner group. The Stoner group believed that magnetism was as described by the Stoner theory, just a uniform change in the discrepancy in the band system, up and down, and Herring and I, to some extent, put that together and said, “Look —”

Hoddeson:

— at what point did this happen?

Anderson:

Well, that was beginning to happen in the early fifties. I remember talking with Scholl and saying, “Look, you ought to look for spin waves in your metallic magnets “because there will be spin waves. There will be fluctuations. Metallic magnets aren’t just sonar theory. Wolfart was just absolutely against this, “No, no, no, the metallic magnet is just uniform magnetization, there’s no fluctive (?) behavior.” Conyars, Herring and Patel, the first paper really on elective motion in metals followed, either the first or the second, simultaneously and independently with Bowman and Kline’s, invented the theory of spin waves in metals. From that point on, Herring kept, every meeting he would give a talk, kind of get his cocktails, you make so and so much (?) and so and so much itinerant, and that will be the theory of magnetism. He had given an example of this, in his work with Patel (Katel?). And his own work in calculating the exchange (?) levels. He was one of the very early structure scientists in many body theory. It has to be ‘55, because it certainly pre-dated the great growth of many body theory in the late fifties. It has to be ‘53 or ‘54. So this was one of the sources of many body theory, with (?) and Brittman. (?)

Hoddeson:

This is Katel and Herring.

Anderson:

Katel and Herring. So that’s important, and Herring’s role in that is important. Domain walls — oh, the ferrites and the garnets, the domain wall motion, we talked a little about that. That really didn’t get re-integrated into physics until the change and the new wave of statistical mechanics of the seventies. Only later, it’s only been realized that the domain wall was the first or the second of the topologicals, the solid talks. But it was the first one where people really thought about this thing as a quantum mechanical object which could move, a dynamical object. Dynamics, quantum mechanics was the dynamics. Mary Walker spent a lot of time thinking about quantum mechanics. School(?) spent a lot of time thinking about it. Another thing that happened at Bell Labs was the nonlinear magnetic resonance business.

Bloembergen and Ryan came out with these strange results on the ferromagnetic resonance of high power levels, and then Harry and I found a — information — let’s see, it was the first hints where Walker and Sewall — but they had the wrong mechanism, and then I pointed out that dipole interactions could do it, and then Sewall carried that on, and it really was the first work on using nonlinear, well, the first work on parametric oscillators and using nonlinear effects for amplification. Later of course then the laser people got a lot farther with that, but this pre-dated the laser. In fact, Harry was busy inventing paramagnetic wissing. (?) The (?) group was busy inventing parametric oscillators, and then along came the maser and the laser and they were out of business. But it was very important theoretically. Bubble memories followed from the Bell Labs, that early Bell Labs work, by Joe Dylan. (pause...)

Hoddeson:

Where did garnets come from?

Anderson:

Where did garnets come from? First I should say, why do I — oh, I know why I associate them, Moran and Seymour Geller — Moran wanted to do oxide, I guess he came from the chemistry department and he was interested in varistors, variable resistors, and then he got interested in these, looking for materials, oxide materials which had very high temperature coefficients of resistance, because that’s what a varistor is. And he discovered that all these vadanium and titanium oxides, there were these gigantic conductivity transitions. So he looked at them and said, “Aha, Mott transitions. I’ll bet these are neutron magnetic.” Well, actually, most of them weren’t, but there was one in there, and again, one of those situations where the neutron people looked and said, “Nonsense, there are no magnetic moments there, “and it turned out that they just didn’t have the accuracy they thought they did, and ten or fifteen years later, B2O3 and several of the others turned out to be magnetic.

But they still are the major examples of metal insulator transitions, these D-band metals or D-band oxides which now we know are really important, because other things happened, like ITC superconductivity. Frank Moran was very early in that. Geller worked on some of those things. Geller was a structural X-ray man, and he and Alton Gilio, I guess, were fooling around with various materials, oxide materials, and they discovered garnets, simultaneously with the French group. And then there was this enormous hassle back and forth about who really had the patents on the garnets and so on. Then Moran and Geller went off to North American, and had a checkered career thereafter, which is irrelevant to the history of magnetism but kind of fun.

Hoddeson:

What happened?

Anderson:

North American was one of these places that thought it would, you know, back in the days when it was fashionable to do so, thought it would re-invent Bell Laboratories. And they really didn’t have the resources. Nobody ever quite realizes how much money Bell Laboratories costs. It’s a very expensive luxury. And the minute something like North American begins to have a little cash flow problem, they close their laboratory and that’s the end of that. So North American was the first of the many, many, many successors who tried to copy Bell Labs and didn’t succeed. I guess none of those were in the group that I taught in ‘54. But Joe Dylan actually was close associated with that and actually still works in bubble memories and that kind of thing. Theory of ferromagnetism, that of course was what Hubbard was about. That I guess is past your cut-off.

Hoddeson:

Well, I’m not sure. Was that about ‘57 or so?

Anderson:

A little later, I would say.

Hoddeson:

A little later?

Anderson:

Yes, ‘59 was when I did my —

Hoddeson:

I don’t know, is there a —

Anderson:

— my super-exchange theory. That had to do with (crosstalk)

Hoddeson:

— carried further.

Anderson:

That had to do with, actually, my second super-exchange theory, that had to do with the fact that I was asked to write a review article for the Seitz-Turnbull (?) series, I guess it was Seitz-Turnbull then, later on — I’m not even sure whether Turnbull was in on it at that time. But I kept putting it off and putting it off. I would start to write, and I would realize I didn’t really understand super-exchange, so I stopped writing. And the summer after I worked on superconductivity, all of a sudden I began to realize what was going on. And that was ‘58, that summer, the super-exchange theory, and that, as far as I know, is the first physical appearance of the Hubbard Hamiltonian. Hubbard came later. Well, one thing which is — well, in that same time, 1959, after I’d done the super-exchange paper, there was one of the perennial reports on the health and welfare of physics. I don’t know whether this was the Pake one or maybe an earlier one. This was material science physics. It was one of these National Academy reports.

There was a panel on magnetism, and I was on that panel, and among other things, there was a meeting in Oxford, which I used that panel to get to, used the money from that panel to get to via NATs, (?) which we used to take in those days, and Bob Schulman was there too, I think also from the panel. That was where I first saw the Friedel theory of resonant states. Friedel talked about it. I have a little theory of ferromagnetism. And it was at that meeting that I made a bet with Walter Marshall that the hyperfine field in iron would turn out to be negative, and won. Which was based on that theory. We all were kind of applying these resonance concepts to, and many body concepts to ferromagnetism. It was kind of the genesis of the Hubbard model approach to ferromagnetism, which then Connamurray, (?) Hubbard himself and so on, lots of people applied and went on with. Hubbard was there. And I think it was, no, it was two years later that I talked to John and he showed me a Hubbard model and his first work with that. Could it have been two years later or could it have been in ‘59? Maybe it was in ‘59 when I visited Harwell.

But it was already after my super-exchange paper, which used the same Hamiltonian but for different purposes. Anyway it was some time after the theory of ferrogmagnetism. There’s a Zener theory. That was great fun. The famous meeting about magnetism where Zener got up and said, someone asked him, “Have you computed these parameters?” and he said, “I don’t need to compute these parameters. Nature is my computer.” But it turned out Zener’s theory wasn’t, the theory of ferrogmagnetism, as far as we know... (off tape) …the Oxford meeting was very seminal in this magnetism business. From it came my ANDERSON model paper.

Hoddeson:

When was that meeting?

Anderson:

‘59. September ‘59. Braznos(?) college.

Hoddeson:

What was that, Zener?

Anderson:

Well, Zener wasn’t.

Hoddeson:

He wasn’t?

Anderson:

Friedel, I think Hubbard, Curti ran the meeting. Sherman. John Owen must have been, Breni must have been, Friedel and Bondell, Blondell and Friedel played a fairly important role in the theory of magnetic impurities. Blondell was always under-estimated. He’s done a lot of important work. (?) was too young. Zeiman must have been there. And Roger Elliot, of course, because it was Oxford. I don’t remember what else, who else. The other thing we were doing, I was doing and Schulman, was — well, not then but within the next year or two — was, we did this work on transferred hyperfine structure, as a way of studying the wave functions of the magnetic ion. I guess John Owen was doing the same thing for the isolated magnetic ions in zinc oxide. John Owen was of course at this meeting. I think he talked about putting one or two manganese ions in zinc oxide and measuring the exchange between them, also measuring the way in which the wave functions spread out into the oxide. The concept of hybridization, (?) ideas about (?) fields and so on. Another line that came from van Vleck is the Megan(?) field theory. Very probably Bauhausen and Argell were the two names in that, especially in using it in chemistry. There’s a whole book by Bauhausen. You can’t really miss that, and Bauhausen has made a big fuss about the history.

Hoddeson:

Why do you say that the meeting was — why was it so pivotal?

Anderson:

Well, I think it, the communication between Friedel and myself, between the two of us and Hubbard, and it’s the first point where I think everyone said to himself, well, if we really can think about the UT , what was then called the UT model, right, and think about the band theory right, maybe in the end we’ll have not only a theory of magnetism but also it was the first meeting where I think that everybody who was there recognized that there is an old-fashioned theory, that the old-fashioned theory of ferromagnetism wasn’t — Stainer and Wolfart must have been there, and so it would have been a very real, there would have been an old guy there too, to argue against. It was that, and then there was this other thing, the idea of transfer of hyperfine structure, and detailed measurement of wave functions of magnetic ions, and that led to Shulman and (?) and so on, and Shulman’s beautiful work on NW 3 and KMNF 3, which you know really showed that the magnetic ion and such and such an admixture with the chlorine and that then communicated in so and so much to the next magnetic ion and so on. Then I talked recently to Shulman, and Art Friedman spent the rest of his life trying to destroy that work. A propos of Art Friedman’s role in the ITC superconductivity, Bob said, “Is he just as bad as he ever was?” and I said, “Yes.” Oh dear.

Hoddeson:

So that pointed the way to —

Anderson:

That pointed the way in a couple of directions. It was the genesis of my thinking about the ANDERSON model. Well, that plus the results on magnetic impurities in superconductors. The question Brent (?) was asking, which was this question of why is iron magnetic in some cases and ruins the superconductivity, in other cases it enhances it? Isn’t there some mysterious thing, he would say. And I would say, “No, no. there’s no mystery. It’s just that we don’t know.” And I tried to explain, I tried to show that there could be magnetic and non-magnetic impurities.

Hoddeson:

Then what next?

Anderson:

Well, that’s really at the end of your —

Hoddeson:

Maybe I’ll have to carry it further, in order to reach a —

Anderson:

Good enough, we always, that’s a good enough — it always seems very chemical and kind of dumb. Bob and I used to say to each other, “Good enough isn’t good enough.” And in fact, he kind of kept on with all this stuff and did a lot of very good stuff over the years. Really good phenomenology. And on oxides in general. It’s all good stuff. And understanding which oxide is doing what, under what circumstances, and really clarified a lot of these metal insulator transitions as being program ionic type transitions, things like that. Most of them really are pretty unglamorous. They’re just appearing transitions of some sort, what’s called nowadays spin pilots. (?) And good enough. So you’ve got that. So, what other subjects are there? There’s the oxides. And there’s the general subject of physics. There’s the Hubbard model, based for that for the Mott transitions, which really didn’t come into fruition until much later. And for theory of ferromagnetism in general. And that again, well, it still hasn’t come into fruition.

Nobody’s really got a good theory of ferromagnetism, but modem work with Hertz and (?) and all kinds of people. And with much better band theory and much better — so, I’m still very dissatisfied with the way things are done. For instance, it’s gotten all cluttered up with people doing — taking their band theory too literally, in the Slater tradition, But that was what was beginning at that time, with Hubbard. Very shortly there was the Goodswilling(?) method and the Kanamori(?) work and Maria by ‘66 had done — well, did this work with Alexander on two Anderson models together, and then they generalized that, and they’ve done a lot of stuff since then, on weak ferromagnetism, which is reasonably satisfactory theory of some varieties of ferromagnetism.

Hoddeson:

I wanted you to comment a little bit on working on the Anderson model and how it was received and things of that sort.

Anderson:

Well, Bent of course didn’t believe a word of it, but Bent never believed any theory. It was aimed at two things. One was, general microcosmic theory of magnetism, to use the UT model, and van Vleck model, and get something out of it. And to try to make sense of Friedel’s ideas. And another was, to answer this question of why iron is magnetic some times and not others. The genesis was really more that, than anything else.

Hoddeson:

When did you start thinking about it?

Anderson:

Well, it was at that meeting, the (?) meeting. Plus, well, it’s Bent’s beginning to do magnetic impurities, which I think was started about that time. Then the idea of the resonant state. They just couldn’t see — also, there were some problems of numbers, really just number problems, and we knew more or less how broad Friedel’s resonances were, and we knew more or less how big the exchange integrals were, and Friedel was just using conventional exchange, Slater, F-1s and Slater Fs and Gs. Excluding, like Slater, excluding the F naught, excluding — he was thinking in old-fashioned Slater terms, that exchange is exchange between hexagonal (?) orbitals, and doesn’t involve any of this big term exchange that’s so important in all these Hubbard model ideas. So I was having trouble believing Friedel, just for numerical reasons. Then I put this theory together, and I discovered two things.

One was that you could use U instead of ordinary exchange integrals, which gained you another magnitude. And the second was that there was this fortuitous factor, Pi squared, and between the two of them I could easily make ions (irons?) magnetic, make oscillated ions magnetic. So it was numbers. Orders of magnitude. But to me it was more important, Friedel’s theory in principle was OK if you just took the exchange to be a general term, but he really clearly meant exchange integrals in the sense of the exchange between two orthon-B (?) ferromagnetic exchange between two orthogonal orbitals, and not the antiferromagnetic type U Hubbard model, U exchange. And it was also, the development was from the super-exchange idea, in that the key thing is the kind of a T squared over U question. In this case T squared over U is the, in a sense, the depth of the level. All these lines came together, but the main one, as far as I was concerned, was numbers. I could get the numbers to work, and Friedel as usual was too vague to really, for there to be solid numerical data. Not too vague. It isn’t Friedel to be too vague. Too offhand, not formal enough. So, that’s where that came from.

Hoddeson:

What happened after that?

Anderson:

People mostly believed it. You know, it seemed to be highly successful. Well, there was this one thing that was perhaps lost in history. Bob Shriefer(?) is a very modest person. It was Bob Shriefer who first really firmly decided that the Anderson model alone, and (?) theory doesn’t work. There were serious problems with quantum fluctuations in the model. And there is a paper, I think, somewhere, by Bob. Also we talked about it a lot, and so, in a sense, he was the first to see that the Anderson model would condolize the theory, be a condo type phenomenon. But that was maybe five or six years later. For the time being, everyone accepted it, and kind of carried out the curve, and we believed that we understood why some irons were magnetic and some weren’t.

Hoddeson:

What happened then?

Anderson:

Not much.

Hoddeson:

Is it still at that point, then?

Anderson:

Well, no. I mean, then of course there was all this business of, the Anderson model isn’t right, because of when you look for it with various kinds of high energy spectroscopy, in terms of how much of the D band with such and such energies, it looks as though you haven’t got U. That there were various numbers involved there and various other interpretations of the data. And I think it has come back again, and people more or less view it as the width is more or less what I said it was and U is more or less what I said it was.

Hoddeson:

OK.

Anderson:

And then also there was all this incredible proliferation of theoretical theory on the fluctuation effects and the condo effects. Yes, that was seminal. That was, the seminal meeting for that was this Pagenot(?) thing. Now, what else? There was something else that I was going to go back to. (pause....) I’m trying to think about Bates. What the crucial contacts were there. Various people that I knew of — I was trying to remember the other day, there was some meeting, I think it may have been Slater and his gang ran a very early meeting on what could be done with inelastic scattering of neutrons, and it was before Brockhause, and they had, at Brookhaven, they had planned to do inelastic scattering, and in the end Brockhause got in ahead of them.

They were just talking about what interesting things could be done, and somehow I remember coming back from that with Show on a train, perhaps to the center of town, and we were talking about how, about just metallic ferromagnets, and he said, “Well, of course, they won’t have any of these spin rates that they were talking about,” and I said, “Nonsense, of course they will.” And whether that was before or after Herring’s work, Herring and Katell, — he had the impression, he was thinking of metallic ferromagnets and ordinary ferrites and things like that, totally different things — there can’t be any fluctuations in the metallic ferromagnets because of the Stoner theory, and the Stoner theory says it’s an exchange constant, it’s everywhere in the metal, and all of a sudden, there is exchange everywhere in the metal, there’s no local dependence. I said, “That’s not true.” Actually, I think already either Bloch or Landauer had introduced a concept of the exchange constant, as the first energy, energy necessary for twisting the magnetization, but nobody had really applied this idea to metallic ferromagnets. It was that idea that Herring then — I didn’t talk about it to Herring. He was interested also in the same problem, and Herring and Katel then applied it to their spin wave theory. Then Herring, as I said, studied the exchange constant in terms of microscopic calculation of it.

But everyone seems to think that Ginsberg, Landauer, was where the idea of the stiffness, an effective free energy with a stiffness constant in it, came from. It seems to have been around and certainly in Herring’s mind, certainly in my mind, because of that conversation with Shaw, quite a number of years before Ginsberg and Landauer at least broke on the consciousness of the West. And anyway, I was using these same ideas in my theories of electricity. Effective microscopic, semi-microscopic interactions, looking at things enlarged but not microscopic scale. It is interesting that we all had that in mind. It’s to be found in one form in Herring’s work, in another form in the early theory of domain walls, and in another form in Ginsberg-Landauer. And that paper on soft modes in paraelectrics was, had similar ideas in it. I had actually finished it up in the early fifties, but I didn’t give it until 1958 in Russia.

Hoddeson:

When you said Ginsberg-Landauer —

Anderson:

The Ginsberg-Landauer is supposed to be the source of the idea that

Hoddeson:

Are you talking about superconductivity? That’s 1960.

Anderson:

That’s ‘50, ‘51. Yet people hadn’t really thought, you know — nowadays, if you go to a meeting about statistical mechanics, people say, “Ginsberg-Landauer free energy” to you. They don’t mean Ginsberg-Landauer of superconductivity. What they mean is a free energy that’s got a gradient turn in it, an effective free energy that’s got a gradient turn in it. Landauer clearly understood that when he did that paper. Nobody else in the world did. Certainly in the West nobody was paying any attention to it, in those terms. I say nobody, but, very few people. Landauer also had the same idea I think in his work on Brock walls, the effective stiffness constant tells you the exchange, how the exchange energy varies with gradients of the magnetization. But maybe the Russians understood it and maybe not. I doubt it. Certainly nobody in the West had this feeling. And these people in magnetism, the Stoners and (?) and all these people that believed in them, just thought, well, it’s either ferromagnetic or it isn’t, it doesn’t twist. So that the existence of that kind of free energy was not properly understood. And correspondingly, when I first began thinking about ferroelectrics, and went to Bell Labs, ‘49, I was still deriving things like that without really realizing that it was new even, or that it wasn’t part of physics. And that’s an interesting point, I think. Certainly the experimental physicists who were doing neutrons — the idea that that was a general way of thinking didn’t come till much later. Landauer-Ginsberg was thought of as a specific theory for superconductivity, not as a general concept which it only became much later. I think because Wilson called it that.

Hoddeson:

I see. Well, you know —

Anderson:

— and if it had any origin, any origin to the concept, in people’s minds, it really was not Landauer-Ginsberg, but Landauer’s earlier work on domain walls. And then the stiffness constant, which came into people’s minds through Herring’s work on the stiffness constant, at least came into my mind, and I think I was probably there a long way before anyone else. Landauer-Ginsberg just didn’t penetrate to the American consciousness, or Europe, the whole Western consciousness, until much much later.

Hoddeson:

So it played quite a peculiar role in the history of superconductivity —

Anderson:

Yes.

Hoddeson:

It doesn’t really, one could have left it out, in a sense.

Anderson:

Yes, except —

Hoddeson:

— and still gotten to, well, they could have gotten to VCS without it.

Anderson:

Yes.

Hoddeson:

I mean, it almost looks, in looking at the history, and of course I wasn’t there, so I don’t —

Anderson:

It came in the wrong order.

Hoddeson:

Yes, in some sense it’s a little like a Bohr atom theory, you know. If VCS could be reduced to Ginsberg-Landauer, then one believed VCS later.

Anderson:

That’s right.

Hoddeson:

But you know, if it hadn’t happened, I mean.

Anderson:

That’s right, not because it wasn’t important, because it was the right phenomenological theory of superconductivity, just as, I don’t know, Bloch and Landauer were the right phenomenological theory of ferromagnetism. I remember seeing Conyers write down this free energy and — (crosstalk) well, I don’t know, who was it that first wrote down? Maybe it was also Ginsberg and Landauer. I’m not sure. It may have been Ginsberg and Landauer. Ferromagnetism.

Hoddeson:

Oh, ferromagnetism?

Anderson:

Ferromagnetism.

Hoddeson:

Of course, Bloch —

Anderson:

Theory of domain walls.

Hoddeson:

No, Bloch. Bloch wrote that.

Anderson:

But Landauer had a lot to do with the domain walls. Bloch wrote down a domain wall but he didn’t say, there’s an energy that depends on the gradient of N. And then I remember, Conyers Herring saying, “There is an energy that depends on a gradient of N.” And that was in ‘53 or ‘54, totally independent of Ginsberg-Landauer and not related to them. That’s an important — well, it’s a tremendously important thing that got re-invented. It’s like topological defects, it kept getting re-invented for each individual instance. And the cleanest one was (?) who did one of the early ones, and got the name on it. But I think the earliest by far was the one by theory of domain walls and ferromagnetism, back in the thirties, which nobody thought of as anything new, because in a way he was just writing elasticity theory for magnetism.

Really of course the first one was elasticity. That’s the first Ginsberg-Landauer theory. And Conyers I think just really thought of himself as writing down elasticity theory. And now it’s called Ginsberg-Landauer, for no particular reason. Well, partly because Ginsberg-Landauer were the first people who said, “Let’s expand around the critical point.” Only because they were stuck, they didn’t have anywhere else to expand it, not because that was really the right thinking or the right place to work.

Hoddeson:

Landauer did that earlier, didn’t he, in the theory of phase transitions?

Anderson:

No. Did he have gradient terms in his?

Hoddeson:

I don’t really remember it well enough.

Anderson:

There was a (?) paper and there was a Landauer paper. It may have had gradient terms in it.

Hoddeson:

I seem to remember that Landauer had a theory of phase change paper.

Anderson:

There must have been gradient terms in it. Because he gets exchange energy out of it.

Hoddeson:

One has to look it up.

Anderson:

Yes. Yes, I guess that’s true. It’s just strange that it’s called Ginsberg-Landauer rather than Landauer-Ginsberg, because it was — it must have been in Landauer’s theory of phase transformations and it must have been in all kinds of other things.

Hoddeson:

I suppose it goes back even to the Bloch domain wall paper, had something like that in it.

Anderson:

It may. Certainly Conyers always called it the Bloch-Wall thing.

Hoddeson:

And he’s the one who knows.

Anderson:

And he’s the one who knows.

Hoddeson:

The Bloch-Wall paper was in 1932 or ‘33.

Anderson:

Yes.

Hoddeson:

Really early.

Anderson:

Yes. I’m sure there was also a Landauer paper on ferromagnetic domain walls very early.

Hoddeson:

I’ve never read that one.

Anderson:

With someone, one of those guys, Pieirls or Ginsberg or Bloch or whoever, — because Landauer refers back to that when he does Ginsberg-Landauer, because it’s again looking at the wall between two different phases. It isn’t the same, but it also has the wall concept. So, what do we have, there’s resonance — we didn’t talk very much about, we talked a little bit about Tubo, and exchange narrowing and all that stuff. First exchange narrowing paper was Gorter and van Vleck, of course, when Gorter was in Harvard in ‘47 giving that lecture course. Mostly narrowing of course was Lindberg and Purcell and Townes, that kind of thing, but I think that van Vleck must have played a major role in their getting that straight. Bloch wasn’t much interested in that kind of thing, and he did magnetic resonance.

He was interested more in the dynamics, not in using it as a tool for studying motions in liquids and solids and things of this kind. Bloembergen did a lot of that, but not all of it. Certainly introduced the concept of motional narrowing. I did my exchange narrowing paper, and then I wrote this general paper in Japan on both exchange and motional narrowing. And as I said, Tubal took over. Tubal-Komida(?) and then he generalized that into a theory of kind of a fluctuation dissipation theory, and Karen and Welton really called the fluctuation, you know, it is their right, they wrote down the fluctuation dissipation integral. On the other hand, people had been using these ideas all along, particularly Tubal and various other people. There’s always Finebog and the attempt to understand the various narrowing phenomena. Oh, what about spin echo? Does that (?) Have you got Hahn in there, was he?

Hoddeson:

Who?

Anderson:

Hahn, Erwin Hahn. Did he fit in that time frame? I don’t remember when spin echo came along. It must have, because we were already, were we? I don’t remember. No, he has to have been just a little later. He developed the passage cases and things like that, in the mid-fifties. He was working closely with George Fayer. But we really didn’t do spin echo nor were we very interested in it, when it did come. George was much more interested in doing field physics with resonance techniques, rather than doing these pretty tricks. You can do it, now it’s a very useful technique for studying relaxation phenomena. Initially it just looked like a pretty trick. A lot of magnetic resonance work history was destroyed by Obergaum. Obergaum wrote this book about magnetic resonance, and he said he didn’t approve of trying to do all this reference writing, so he was going to leave all the references out of his book, and just write a book as though the subject was brand new.

Hoddeson:

Oh no. So why do you say it was destroyed?

Anderson:

And so everyone thereafter referred to Obergaum, and all the references disappeared from the literature.

Hoddeson:

We may have to re-discover.

Anderson:

It will have to be rediscovered.

Hoddeson:

You didn’t comment much on Katel.

Anderson:

I thought I had.

Hoddeson:

A little bit. Maybe that’s enough. I don’t know.

Anderson:

No, he was, I said, he set up the Berkeley group. He was the leader of what magnetism got started in — well, not the leader, because the principle, Bozarth was the leader at Cal, but the fact is, Bozarth was interested in completing his book, and Charlie was the person who was defending the magnetism effort, against two things. One of them was the overwhelming effect of the transistor, kind of taking over everything, and the second was Bozarth, who wanted to finish his book. So Charlie defended Williams, he defended me, he defended the little magnetic resonance group that we had, Galt and Yager. I think he had left already in ‘52, didn’t he, or something like that, very early. But by then, there was, it was more or less established, and then they set up this Clarkston group.

I guess it left, the nucleus of that was Clarkston and Walker. He’d been working on traveling wave tubes. I think the company had come to the conclusion that the maser and the laser or something like that was going to supersede traveling wave tubes, so they said to these guys, “Retrain yourself in something,” and they decided on magnetism, and they were thereafter the Clarkston group, always thought of as a group of eager young men traveling in lockstep. Not that Walker ever traveled in lockstep with anyone or Harry Sewall, but the rest of them did, Jack Greeno, Clarkston, (?) and so on. And then they took over the —

Hoddeson:

But you know, Bozarth’s whole approach to physics is so different from —

Anderson:

— yes, he’s a materials man.

Hoddeson:

— from that of the other people. I mean, it’s from a completely classical point of view.

Anderson:

Yes. Yes, he wasn’t interested in the quantum mechanics of ferromagnetism. He was interested in putting alloys together.

Hoddeson:

How could he have had any control at all?

Anderson:

Because he was one of the first two or three real solid state physicists at the laboratories. He had been very strong in terms of position, and he knew everybody everywhere and was a friend of van Vleck’s. And he was a gentleman and a scholar, and he had a delightful wife. Terrible man himself, in fact. But he was just very influential with the powers that be, and he’d been there longer than anyone, and he knew everyone, and he was a good friend of Mervyn Kelly’s. He actually took up with Mervyn Kelly’s wife that year. You knew that? But what was so important about Katel with the Berkeley group, in the first place, his influence on Galt and myself. Also the Berkeley group, he went there as — arrived in Berkeley as the successor to one of these people who had left because of the oath. He was the first scab. He wasn’t really a scab, because he never signed the oath.

They had stopped the oath when he arrived. He inherited all these students that these people had, who were very good. There was Oberhausen and there was Merle Cohen and there was Abrahams and two or three others who were very good, Fred Keppler. So he had about six or eight students to work with, and he had Kipp, who then had a lot of — Berkeley’s always had great solid state students, so Keppler had. Kipp had in rapid succession Cortes and Fayer and I don’t remember, but Walter Knight came, a tremendously powerful group of experimentalists who rapidly developed. And it was just an incredible combination of people doing very exciting things. They did the Oberhausen effect. They did the cyclotron resonance work, in which they beat out Fay Soule who was trying to do it in Bell Labs at the same time. Cyclotron resonance, semiconductors, then they happened to get to Russia very early after the thaw, and came home with the Aswald-Kaner(?) idea. They got that going very rapidly.

And they started up the — they also were very good at getting post-docs from England, because the Englishman of course wants to go to the sunniest possible place. If he’s going to come to the United States, he might as well get some sun. So he had Roger Elliot and he had Owen, John Owen, who’s terrific, and he had two or three others. He also got a lot of post-does through just on general principles, and he had this fund that he got set up so that he could hire people like, first, Dyson, and then I went out there in ‘58, and took a summer professorship that he had at his disposal. Dyson worked for two summers on magnetism problems with Charlie. Did you know that?

Hoddeson:

No. Absolutely not.

Anderson:

Well, there’s two marvelous papers, one on the magnetic relaxation in metals, moving electrons, very subtle, very beautiful piece of mathematics. And the second one was on spin waves. Justification of the use of spin waves. And also a justification of the fact that the second term after T to the 3 I’s is T to the 4th. It’s successive. You can get the same results in much simpler terms. But at the time it looked pretty wonderful. But the other isn’t successive.(?) You really do need to do that mathematics, and Dyson did it and it was beautiful.

Hoddeson:

I must look at those.

Anderson:

‘56 and ‘57, then in ‘58, Dyson was busy down at General Dynamics, so Charlie brought me in, and that was the year I did my big paper on gauge invariance. Finished it there, and started the paper on super-exchange. So, Charlie had a real powerful thing going, and they started spin glasses. They did the Oberhausen effect. They did the semiconductor and metal cyclotron resonance work. There was the night shift work they did. I said, the Oberhausen effect. Fayer came from there, was trained there, but then he did his best stuff at Bell Labs, endor(?) and all that. Portus wrote the paper that stimulated me to do localization, because he made the mistake of assuming that the average breadth is equal to the real breadth, and it’s equal to 1 over T 1. But Portus did this beautiful study of various passage phenomena. A very under-estimated physicist. It was very good, for a while. And the experimental end of it continued to be good, still continues to be good. But Charlie just couldn’t ever get along with another theorist of equal power. Couldn’t get along with me. And he had a lot of good people in there temporarily. He had Jim Phillips in there temporarily. He had John Hopfield in there temporarily, in his post-doc assistant professor...

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