Driving mechanism for damping and g-factor in non-amorphous ferromagnetic CoFeZr ultrathin films

¹ Laboratoire de Magnétisme de Bretagne, CNRS, Université de Bretagne Occidentale - 6 avenue le Gorgeu, 29285 Brest Cedex, France
² CEMES-CNRS - 29 rue Jeanne Marvig, 31055 Toulouse, France

^(a) david.spenato@univ-brest.fr

Received: 10 May 2016
Accepted: 1 July 2016

Abstract

We demonstrate that an in-plane uniaxial anisotropy may be induced in non-amorphous soft CoFeZr films. We used broadband ferromagnetic resonance spectroscopy and complex permeability spectra to investigate the spin dynamics in CoFeZr films. We report a systematic study of the FM thickness on the fundamental dynamic parameters such as the effective magnetisation, the g-factor and relaxation mechanisms. Our study reveals that the decrease of the effective magnetisation mesured with FMR with thickness is not due to perpendicular anisotropy but to low dimentionality. Moreover, we observed a decrease of the g-factor with thickness and a modification of the ratio of the orbital to the spin magnetic moment. These films exhibit good high-frequency performance red (i.e. high permeability in a broad frequency range and a low damping) at low thickness of about a few nanometers.