Efficient switching of magnetization using spin-orbit torque

• Speaker: Prof. Byong-Guk Park (KAIST)
• Date: Wednesday, February 22, 2017, at 17:00
• Place: Jungho Seminar Room

Spin-orbit torque (SOT) arising from the spin-orbit coupling of non-magnetic heavy metals have gained much attention because it allows electrical switching of perpendicular magnetization as well as high speed domain wall motion. In the ferromagnet (FM)/non-magnetic heavy metal (HM) structure, in-plane current generates spin accumulation at the FM/HM interfaces via spin Hall effect and/or interfacial spin-orbit coupling, which gives rise to a torque to the FM layer. However, there are two requirements for realization of the SOT-based spintronic devices: reduction of the critical current for the magnetization switching and removal of the additional in-plane magnetic field for deterministic switching.

In the first part of the talk, I present the enhancement of the SOTs in HM/FM oxide structures with two approaches: controlling the resistivity of the Pt HM layer and introducing Ti interfacial layer at the Pt/CoFeB structures. These improve the SOT- induced switching efficiency by modulating the bulk spin Hall effect and/or interfacial spin-orbit coupling contribution.

In the second part, I report the SOTs in the structures of antiferromagnets (AFM) IrMn/FM CoFeB, where the AFM is replaced with HM layer. The AFM IrMn can generate a sizable SOT as well as effective magnetic field via exchange bias, which allows the field-free magnetization switching.