Magnetization switching by spin-orbit torque in crystalline (Ga,Mn)(As,P) film deposited on a vicinal GaAs substrate

Current-induced spin-orbit torque (SOT) switching of magnetization in a crystalline (Ga,Mn)(As,P) ferromagnetic semiconductor (FMS) film grown on a vicinal GaAs substrate is investigated. The FMS film has four magnetic easy axes along the $\ensuremath{\langle}100\ensuremath{\rangle}$ directions in the $(001)$ crystal plane. However, unlike FMSs such as (Ga,Mn)(As,P) grown on the $(001)$ surface, in vicinal configuration, both in-plane and out of plane components of magnetization contribute to Hall resistance (HR). Thus the values of the HR are different when the magnetization is aligned along the different easy axes owing to the inclination of the film plane away from the $(001)$ crystal plane. Current-induced magnetization transitions between easy axes are clearly observed in HR measurements in the absence of an external magnetic field, resulting in HR hysteresis loops as the current is scanned. Each hysteresis loop, however, reveals different stable states. The HR values corresponding to these states indicate that magnetization transitions between the adjacent easy directions are partial, the stable states being composed of sets of multiple domains magnetized along different easy directions. The stable states observed during the SOT magnetization switching are highly reproducible over a large number of current scans. The field-free multivalued SOT magnetization switching observed in such vicinal (Ga,Mn)(As,P) FMSs suggests the possibility of using vicinal FMS films for current-controlled, energy-efficient magnetic multinary memory devices.