Perpendicular standing spin wave and magnetic anisotropic study on amorphous FeTaC films

TL;DR

This study investigates the magnetic anisotropy and spin wave excitations in amorphous FeTaC films of varying thickness using MS-FMR, revealing how exchange stiffness and magnetic parameters evolve with film thickness.

Contribution

It provides a detailed analysis of spin wave modes and magnetic parameters in amorphous FeTaC films, including the first observation of PSSW modes in these films and their dependence on thickness.

Findings

PSSW modes observed in films thicker than 50 nm.

Exchange stiffness increases with film thickness.

Magnetic parameters modeled successfully using dispersion relations.

Abstract

Magnetic anisotropy, spin wave (SW) excitation and exchange stiffness constant of amorphous FeTaC ($d$ = 20-200 nm) films were studied as a function of thickness using micro-strip ferromagnetic resonance (MS-FMR) technique. The MS-FMR spectra for in-plane applied magnetic field show the presence of uniform precessional mode ($n$ = 0) along with first perpendicular standing spin wave (PSSW) mode ($n$ = 1) especially for $d$ = 50, 100 and 200 nm films. The angular ($\varphi_{H}$) dependence of resonance field ($H_{r}$) and magnetic field dependence of resonance frequencies ($f_{r}$) in planar configuration for the uniform and PSSW modes were modeled successfully by using dispersion relation which arises from a combination of exchange and dipolar interactions. The relevant parameters such as saturation magnetization ($4\pi M_{S}$), uniaxial anisotropic constant ($K_{u}$), $g$-factor, and exchange stiffness constants ($A_{ex}$) are estimated for different FeTaC film thickness. $A_{ex}$ is found to increase from 1.52(4)$\times$10$^{-7}$ to 5.0(5)$\times$10$^{-6}$ erg/cm as the thickness of film increases from 50 to 200 nm, possibly due to surface pinning effect or significant inhomogeneity especially at higher thickness films.