Table of Contents
ISRN Condensed Matter Physics
Volume 2012, Article ID 387380, 12 pages
http://dx.doi.org/10.5402/2012/387380
Research Article

Micromagnetic Simulation of Spin Transfer Torque Magnetization Precession Phase Diagram in a Spin-Valve Nanopillar under External Magnetic Fields

1Department of Physics, University of Science and Technology Beijing, Beijing 100083, China
2Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, USA

Received 29 May 2012; Accepted 21 June 2012

Academic Editors: N. Birge and A. A. Kordyuk

Copyright © 2012 H. B. Huang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We investigated spin transfer torque magnetization precession in a nanoscale pillar spin-valve under external magnetic fields using micromagnetic simulation. The phase diagram of the magnetization precession is calculated and categorized into four states according to their characteristics. Of the four states, the precessional state has two different modes: steady precession mode and substeady precession mode. The different modes originate from the dynamic balance between the spin transfer torque and the Gilbert damping torque. Furthermore, we reported the behavior of the temporal evolutions of magnetization components in steady precession mode at the condition of the applied magnetic field using the orbit projection method and explaining perfectly the magnetization components evolution behavior. In addition, a result of a nonuniform magnetization distribution is observed in the free layer due to the excitation of non-uniform mode.