Observation of anti-damping spin-orbit torques generated by in-plane and out-of-plane spin polarizations in MnPd3

TL;DR

This study demonstrates unconventional spin-orbit torques in MnPd3 thin films enabling magnetic switching without external magnetic fields, advancing spintronic device capabilities.

Contribution

The paper reports the discovery of out-of-plane and in-plane anti-damping-like torques in MnPd3, allowing magnetic switching without external magnetic fields, a novel finding in spin-orbit torque research.

Findings

Observation of out-of-plane and in-plane anti-damping-like torques at room temperature.

Complete magnetic switching achieved without external magnetic fields.

Spin polarization origins linked to low symmetry of (114) MnPd3 films.

Abstract

High spin-orbit torques (SOTs) generated by topological materials and heavy metals interfaced with a ferromagnetic layer show promise for next generation magnetic memory and logic devices. SOTs generated from the in-plane spin polarization along y-axis originated by the spin Hall and Edelstein effects can switch magnetization collinear with the spin polarization in the absence of external magnetic fields. However, an external magnetic field is required to switch the magnetization along x and z-axes via SOT generated by y-spin polarization. Here, we present that the above limitation can be circumvented by unconventional SOT in magnetron-sputtered thin film MnPd3. In addition to the conventional in-plane anti-damping-like torque due to the y-spin polarization, out-of-plane and in-plane anti-damping-like torques originating from z-spin and x-spin polarizations, respectively have been observed at room temperature. The spin torque efficiency corresponding to the y-spin polarization from MnPd3 thin films grown on thermally oxidized silicon substrate and post annealed at 400 Deg C is 0.34 - 0.44. Remarkably, we have demonstrated complete external magnetic field-free switching of perpendicular Co layer via unconventional out-of-plane anti-damping-like torque from z-spin polarization. Based on the density functional theory calculations, we determine that the observed x- and z- spin polarizations with the in-plane charge current are due to the low symmetry of the (114) oriented MnPd3 thin films. Taken together, the new material reported here provides a path to realize a practical spin channel in ultrafast magnetic memory and logic devices.