Approximate Theory of Microwave Generation in a Current-Driven Magnetic Nano-contact Magnetized in an Arbitrary Direction

Published

April 1, 2005

Author(s)

Pavel Kabos, Andrei N. Slavin

Abstract

An approximate analytic theory of microwave generation by spin-polarized direct current in a magnetic nano-contact magnetized in an arbitrary direction is developed. It is shown that whent he spin-transfer torque caused by spin-polarized current compensates the natural magnetic dissipation in a "free" layer of the nano-contact a quasi-uniform precession of magnetization about the direction of the internal bias magnetic field is excited. With the increase of the current magnitude the angle of precession increases, making precession nonlinear, and reducing the project Mzof the precessing magnetization vector on the precession axis (z-axis). This reduction of Mz is responsible for the nonlinear limitation of the precession amplitude and for th nonlinear frequency shifts of the generated microwave oscillations. Due to the influence of demagnetizing fields in the "free" layer the nonlinear frequency shifts have different magnitudes and signs for different orientations of the external bias field He. The theory gives good qualitative and even partly quantitative explanation of the main part of microwave magnetization dynamics experimentally observed in magnetic nano-contacts.

Citation

IEEE Transactions on Magnetics

Volume

41

Issue

4

Pub Type

Journals

Keywords

Magnetism, spin momentum transfer, spin waves, nonlinear threshold, microwave radiation

Citation

Kabos, P. and Slavin, A. (2005), Approximate Theory of Microwave Generation in a Current-Driven Magnetic Nano-contact Magnetized in an Arbitrary Direction, IEEE Transactions on Magnetics (Accessed May 15, 2025)