Quantitative characterization of current-induced self-spin-orbit torques in a perpendicularly magnetized (Ga,Mn)As single thin film

Quantitative characterizations of the current-induced spin-orbit torques (SOTs) are vitally important for both fundamental understanding and practical applications of SOT-based spintronic devices. Here, we study effective SOT magnetic fields in a (Ga,Mn)As single film with perpendicular magnetic anisotropy, where we can achieve highly efficient full-magnetization switching with a small critical switching current density J_c as low as 10⁵ A/cm². Using second harmonic Hall measurements, we estimate the SOT effective fields; the damping-like SOT effective field H_DL and the field-like SOT effective field H_FL are 22.1 and 18.1 Oe, respectively, at 4 K when a current of 1.43 × 10⁵ A/cm² is applied to the device. Based on this result, we estimate the corresponding spin-torque efficiencies ξ_DL and ξ_FL to be 1.32 and 1.08, respectively, which are one order of magnitude higher than those in conventional metal systems. The high efficiency can be partly attributed to the simple single-functional-layer structure, which can avoid the loss from spin scattering at the interface between different functional layers as observed in conventional SOT devices. Our findings will lay the foundation for studying SOT physics and devices based on ferromagnetic semiconductors.