The Study of Structure-Dependent Properties of Thin Magnetic Films at Microwaves by Field-Domain Resonance Technique

Abstract

Abstract-The strip-line frequency-domain technique for permeability measurement is compared to the field domain technique. The combined setup for microwave measurement of thin film permeability with both techniques is proposed. The field-domain technique is less affected by inhomogeneity of measurement strip cell and has significantly higher signal-to-noise ratio, but the obtained parameters are affected by film thickness and may differ from that of the frequency-domain technique. Analysis of the field-domain data obtained at a set of frequencies makes it possible to determine the saturation magnetisation, the anisotropy field and the damping factor without the knowledge of the amount of substance under study. In case of a simple permeability spectrum the data on metal thickness make it possible to estimate the effective skin-depth as well. The technique is tested by simulation and is applied to determine permeability of Fe-based films vacuum-sputtered on glassceramic and polymer substrates.

A contribution from the magnetoelastic effect to measured microwave permeability of thin ferromagnetic films

“…This field is constituted by the crystallographic anisotropy field, H a , external static magnetic field, H 0 , and magnetoelastic field, H l ¼(3ls/2M 0 ), with l and s being the magnetostriction constant and the uniform tension in the film. A convenient tool for estimating microwave magnetic performance from the measured frequency dependence of permeability is Acher's factor introduced as A¼(m s -1)f r 2 /(g4pM 0 ) 2 [5,11]. It is seen from (1) that AE1 for the permeability attributed to the ferromagnetic resonance in a film magnetized uniformly in plane and measured in the direction perpendicular to the easy axis; otherwise Ao1.…”

“…Hence, for measurements of unsaturated films, a frequency range of up to several GHz is usually considered as sufficient. However, expanding of this frequency range is needed, e.g., for studies of film behavior under an external magnetic bias, which is a useful tool for understanding the magnetic structure of the films [11].…”

Frequency dependence of microwave complex permeability under magnetic bias

“…However, samples of the coaxial form are nonuniformly magnetized, in contrast to samples of ellipsoidal shape. The response of such samples to the external bias is described by a sum of depolarization factors [6]. Often an effective depolarization factor, which depends not only on the shape and orientation of the sample, but also on its permeability, is used [7].…”