Nonlinear ferromagnetic resonance shift in submicron Permalloy ellipses

Published

February 27, 2015

Author(s)

Feng Guo, Lyubov Belova, Robert D. McMichael

Abstract

We report a systematic study of nonlinearity in the ferromagnetic resonance of a series of submicron Permalloy ellipses with varying aspect ratios. We focus on the sign of the foldover, a resonance field shift or frequency shift that occurs with high excitation powers. Using ferromagnetic resonance force microscopy, we find that the foldover changes sign as a function of anisotropy field and applied field in qualitative agreement with a macro-spin analysis. However, both measurement and micromagnetic modeling results exhibit values of the nonlinear coefficient that are more positive (i.e. the foldover tends toward low field) than are predicted by the macrospin model. We attribute the difference to the non-uniformity of the precession modes in the ellipses. The results are useful in understanding nonlinear physics in nanomagnets and applications of spin-torque oscillators.

Citation

Physical Review B

Volume

91

Issue

6

Pub Type

Journals

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DOI Link

Keywords

precession, nonlinear, nanomagnet, ferromagnetic resonance force micrsocopy, FMRFM

Citation

Guo, F. , Belova, L. and McMichael, R. (2015), Nonlinear ferromagnetic resonance shift in submicron Permalloy ellipses, Physical Review B, [online], https://doi.org/10.1103/PhysRevB.91.064426 (Accessed April 18, 2024)