Room-temperature magnetoresistance achieved in a metallic antiferromagnetic material

Electronics developers are looking to reduce the energy consumption of devices by utilizing electron spins. Conventional spintronic devices use ferromagnets (FMs) to actively store information, but problems arise when shrinking FMs to the 10-nanometer scale. Antiferromagnets (AFMs) are alternative materials that could realize high-speed, nonvolatile and scalable architectures.

To this end, DuttaGupta et al. investigated magnetoresistive effects for reading data from an important metallic AFM material. They investigate a metallic AFM heterostructure with industrial potential, i.e., room-temperature operation and ease of fabrication.

The authors combined an AFM platinum-manganese (PtMn) layer with nonmagnetic Pt in a PtMn/Pt bilayer using magnetron sputtering techniques. They subsequently patterned the bilayer into Hall-bar devices by photolithography and argon-ion milling. Then, they measured the longitudinal magnetoresistance under magnetic field rotations along three mutually perpendicular directions.

To do this, the authors applied a magnetic field and current to the material while rotating along x-y, y-z and x-z axes. “The angle between the current and magnetic field changes and this introduces a change in the property of the sample which we quantify measuring the resistance,” said DuttaGupta.

This is the first time appreciable magentoresistive effects have been shown in an all-metallic AFM bilayer system and is thought to be caused by generation of spin current in the nonmagnetic Pt layer which is subsequently absorbed by the AFM layer. “We believe this could be a way to read written information out of an AFM metal,” said DuttaGupta. The authors are now using current to manipulate the AFM and prove that information can be written onto the material.

Source: “Angle dependent magnetoresistance in heterostructures with antiferromagnetic and non-magnetic metals,” by S. Dutta Gupta, R. Itoh, S. Fukami, and H. Ohno, Applied Physics Letters (2018). The article can be accessed at https://doi.org/10.1063/1.5049566 .