Planar spin-transfer device with a dynamic polarizer

摘要

In planar nano-magnetic devices magnetization direction is kept close to agiven plane by the large easy-plane magnetic anisotropy, for example by theshape anisotropy in a thin film. In this case magnetization shows effectivelyin-plane dynamics with only one angle required for its description. Moreover,the motion can become overdamped even for small values of Gilbert damping. Wederive the equations of effective in-plane dynamics in the presence ofspin-transfer torques. The simplifications achieved in the overdamped regimeallow to study systems with several dynamic magnetic pieces (``free layers'').A transition from a spin-transfer device with a static polarizer to a devicewith two equivalent magnets is observed. When the size difference between themagnets is less than critical, the device does not exhibit switching, but goesdirectly into the ``windmill'' precession state.