Efffcient Spin−Orbit Torque Switching in a Perpendicularly Magnetized Heusler Alloy MnPtGe Single Layer

Abstract

Electrically manipulating magnetic moments by spin−orbit torque (SOT) has great potential applications in magnetic memories and logic devices. Although there have been rich SOT studies on magnetic heterostructures, low interfacial thermal stability and high switching current density still remain an issue. Here, highly textured, polycrystalline Heusler alloy MnxPtyGe (MPG) fflms with various thicknesses are directly deposited onto thermally oxidized silicon wafers. The perpendicular magnetization of the MPG single layer can be reversibly switched by electrical current pulses with a magnitude as low as 4.1 × 1010Am−2, as evidenced by both the electrical transport and the magnetic optical measurements. The switching is shown to arise from inversion symmetry breaking due to the vertical composition gradient of the fflms after sample annealing. The SOT effective ffelds of the samples are analyzed systematically. It is found that the SOT efffciency increases with the fflm thickness, suggesting a robust bulk-like behavior in the single magnetic layer. Furthermore, a memristive characteristic has been observed due to a multidomain switching property in the single-layer MPG device. Additionally, deterministic ffeld-free switching of magnetization is observed when the electric current ffows orthogonal to the direction of the in-plane compositional gradient due to the in-plane symmetry breaking. This work proves that the MPG is a good candidate to be utilized in high-density and efffcient magnetoresistive random access memory devices and other spintronic applications.