Spin-transfer induced dynamic modes in single-crystalline Fe-Ag-Fe nanopillars

We present measurements and simulations of spin-transfer torque (STT) induced magnetization dynamics in nanopillars containing a thin, circular, single-crystalline Fe nanomagnet with four-fold in-plane magnetocrystalline anisotropy as a free layer. The magnetoerystalline anisotropy inherent to bcc-Fe allows for a consecutive switching of the magnetization by 90[degrees] between parallel and antiparallel alignment to the fixed layer magnetization. Additionally, the anisotropy gives rise to steady-state precession of the magnetization at low or even zero applied magnetic field as well as at large fields exceeding the coercive field. While the low-field mode is governed by the interplay between the STT and the anisotropy, the high-field dynamics result from the STT acting against the externally applied magnetic field. Index Terms--Magnetization dynamics, magnetoerystalline anisotropy, nanomagnet, spin-transfer torque.