Large Magnetoresistance in antiferromagnet tunnel junctions

Abstract

Antiferromagnets (AFM’s) have been used in spintronics devices so far only to pin the magnetization direction of a ferromagnetic electrode through the exchange-bias effect. Spintronics devices whose transport is governed by AFM’s have been theoretically proposed, but remain a great challenge for experimental realization. Here, we demonstrate a large magnetoresistance effect in a tunnel junction with an AFM electrode of IrMn and a nonmagnetic counter electrode [1]. In the device, the tunneling resistance depends on the magnetization direction of the IrMn electrode, so-called tunneling anisotropic magnetoresistance (TAMR) effect, which is based on the spin-orbit coupling. This is quite different from the conventional spin-valves where the resistance depends on the relative magnetization directions of two ferromagnetic electrodes. The magnetization direction of the AFM IrMn layer was manipulated with a relatively small magnetic field of 50mT by the exchange spring effect of coupled soft NiFe. In addition, the AFM TAMR provides a means to study the exchange-bias effect by an electronic transport measurement [2].