Multidirectional available high-frequency response with zero-field resonance above 8 GHz in epitaxial α-Fe(001) films

Abstract

We investigate the high-frequency characteristics of epitaxial single crystal α-Fe(001) thin films by permeability spectroscopy with microwave transmission along different in-plane crystal directions. The results show an in-plane isotropic static permeability above 50 with a multidirectional zero-field resonance frequency ( f r ) higher than 8 GHz in the films. We demonstrate that these multidirectional available high-frequency characteristics result from the strong magnetocrystalline anisotropy in the films and not from other kinds of magnetic anisotropies. The study on thickness-dependent films show f r being stable at 8.4 GHz in the films thicker than about 20 nm.

Extremely High Ferromagnetic Resonance Frequency Induced by Triclinic Lattice Distortion in Epitaxial FeCo/MgAl2O4 (001) Films

“…[ 25 ] There are however limited reports on the application of metal single‐crystal films as self‐biased SMFs. [ 26 ] The main reasons are: 1) the intrinsic magnetocrystalline anisotropy constant K of commonly used SMFs is very small. For example, K of bulk Fe is about 42–48 kJ m −3 , and the corresponding H K is only about 500 Oe.…”

“…Most of the samples show two resonance peaks. Peak I at low frequency of around 8 GHz can be assigned to the intrinsic FeCo resonance, [ 26 ] while peak II at high frequency shows a strong thickness dependence, and dramatically increases from 12.4 GHz in the 100‐nm film to 40 GHz in the 21‐nm film (Figure 3a). Due to the limited frequency of the vector network analyzer in our laboratory, the presence or absence of peak II for films thinner than 21 nm is not detectable at present.…”