09:15 〜 09:30
▼ [20a-131-2] Efficient full spin-orbit torque switching in a single layer of a perpendicularly-magnetized ferromagnetic semiconductor GaMnAs
キーワード：spin-orbit torque, magnetization switching, GaMnAs
Spin-orbit torque (SOT) magnetization switching has been proposed to optimize the performance of magnetoresistive random access memory (MRAM) devices on the readability, access latency, and energy consumption. In the conventional SOT systems, there basically are two functional layers, one of which is the ferromagnetic layer and the other one is the paramagnetic layer with a large spin Hall angle to generate spin current and inject it into the adjacent ferromagnetic layer. Then the spin current exerts a torque on the magnetization of the ferromagnetic layer and reverses it. Therefore, the switching efficiency should be strongly limited by the interface quality and the spin injection process across the interface. Here, we report a highly efficient full SOT switching by applying a current with a density of Jc = 3.4×105 A/cm2 in a single layer of perpendicularly magnetized ferromagnetic semiconductor GaMnAs. With the intrinsic bulk inversion asymmetry of the zinc-blende crystal structure, the intrinsic spin-orbit interactions couple the hole spin with its momentum and generate the Dresselhaus effective magnetic field, which contributes to induce an in-plane component of hole’s spin in the GaMnAs thin film. Then the in-plane spin component exerts a torque on the magnetic moment of GaMnAs thin film itself. We have achieved the magnetization reversal just by driving a current in a single ferromagnetic GaMnAs layer, with much smaller Jc by two orders of magnitude than the Jc values reported so far in metallic bilayer systems. Our finding will provide a new possibility of more efficient SOT switching by using a single-crystalline ferromagnet with intrinsic bulk-inversion asymmetry, large spin-orbit interactions, and spin polarization.