Abstract
The B2-ordered alloy FeRh shows a metamagnetic phase transition, transforming from antiferromagnetic to ferromagnetic order at a temperature Tt∼380 K in bulk. In addition to temperature, the phase transition can be triggered by many means such as strain, chemical doping, or magnetic or electric fields. Its first-order nature means that phase coexistence is possible. Here, we show that a phase boundary in a 300-nm-diameter nanopillar, controlled by a doping gradient during film growth, is moved by an electrical current in the direction of electron flow. We attribute this to spin injection from one magnetically ordered phase region into the other driving the phase transition in a region just next to the phase boundary. The associated change in resistance of the nanopillar shows memristive properties, suggesting potential applications as memory cells or artificial synapses in neuromorphic computing schemes.
Highlights
The doped FeRh film was grown by DC sputtering at 600◦C onto commercially obtained MgO (001) substrates1
Bragg peaks are clearly visible for the (001) reflections of both the NiAl buffer and FeRh film, confirming that B2-ordering is present in both layers
The bottom electrodes and nanopillars were defined using e-beam lithography on a JEOL JBX-6300FS system
Summary
The doped FeRh film was grown by DC sputtering at 600◦C onto commercially obtained MgO (001) substrates. A final anneal at 700◦C for 1 hr in vacuum allowed the FeRh to obtain the proper crystal structure and smooth out the doping profile within the film thickness. Bragg peaks are clearly visible for the (001) reflections of both the NiAl buffer and FeRh film, confirming that B2-ordering is present in both layers. Analysis of the ratio of integrated intensities under the two peaks for the FeRh is consistent with a B2 chemical order parameter S ∼ 0.9, a typical level for a thin film of this material
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