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Practical consequences of spin-motive-forces in magnetic structures

Stewart E. Barnes, University of Miami


A spin-motive-force (smf) reflects the energy conservation requirements of the spin-torque-transfer (stt) process [1]. For domain walls, spin-valves or magnetic tunnel junctions it produces a "back-smf" which drives a spin current which reflecting Lenz’s law apposes the applied "force" be it an electrical current or magnetic field. This effect is of particular importance for highly structures magnetic systems such as those containing magnetic vortices or many domain walls where it will tend to reduce the effect of the stt process and hence relaxation processes. The experimental consequences and applications will be discussed.

 

"Spin-pumping" is usually described [2] as the inverse of the spin-torque-transfer process, i.e., a current produced when e.g. a magnetic free layer is driven by an external radio-frequency field. Such a current source produces voltages due to some interfacial resistance and is non-universal unlike an smf. As will be described, the difference between a spin pumping current and smf voltage source is easily determined by experiment.

 

A spin-battery converts magnetic into electrical via the production of an smf. The requirements of the working material for such a battery will also be discussed.

 

[1] S. E. Barnes and S. Maekawa Phys. Rev. Lett. 98, 246601 (2007)

[2] Yaroslav Tserkovnyak, Arne Brataas and Gerrit E. W. Bauer, Phys. Rev. B 66, 224403 (2002)

 

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