Spin-Transfer-Torque: Antiferromagnets

An electrical current can transfer spin angular momentum to a ferromagnet [1–3]. This novel physical phenomenon, called spin transfer (or spin torque), offers unprecedented spatial and temporal control over the magnetic state of a ferromagnet and has tremendous potential in a broad range of technologies, including magnetic memory and recording. It was recently predicted [4] that current-induced torques are a general property of magnetic metals not limited to ferromagnets (F) and, in particular, that spin torques act on the order parameter of antiferromagnetic (AFM) circuit elements. Unlike spin torques in a F metal, which follow from conservation of total spin and act only near interfaces, current-induced torques in AFM metals are not related to total spin conservation and have a bulk contribution [4].

STT: FeMn/CoFe Original observation

STT in AFMs A brief review

STT: IrMn/CoFe New AFM material

STT: FeMn/CoFe, IrMn/CoFe, IrMn/NiFe New AFM/F pairs

1. Slonczewski, J. C. Current-driven excitation of magnetic multilayers. J. Magn. Magn. Mater. 159, L1-L7 (1996).

2. Berger, L. Emission of spin waves by a magnetic multilayer traversed by a current. Phys. Rev. B 54, 9353-9358 (1996).

3. Tsoi, M. et al. Excitation of a magnetic multilayer by an electric current. Phys. Rev. Lett. 80, 4281-4284 (1998).

4. Núñez, A. S., Duine, R. A., Haney, P. M., and MacDonald, A. H. Theory of spin torques and giant magnetoresistance in antiferromagnetic metals. Phys. Rev. B 73, 214426 (2006).

Supported in part by NSF grant DMR-06-45377