An Avalanche Spin-Valve Transistor

An avalanche spin-valve transistor switches a current "on" or "off" depending on whether the magnetizations of two thin films are parallel (large current) or anti-parallel (small current). Such a spintronic transistor is somewhat like the giant magnetoresistance (GMR) read heads in hard drives, but is 10 to 100 times more sensitive.

The usual drawback of spin-valve transistors, a weak output current, is, in the Harvard lab of Venkatesh Narayanamurti, overcome by using an avalanche process much like the one used in photodetectors---an incoming electron ionizes several secondary electrons, each of which ionizes still more electrons, adding up in the end to a sizable current.

One of the team members, Kasey Russell (kasey.russell@gmail.com, 617-496-5471) says that the extra sensitivity and strong output could lead to use of the device in magnetic storage technologies. (Russell et al., Applied Physics Letters, November 8, 2004; lab website at http://www.deas.harvard.edu/venky/research.html#overview)