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

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 (φH) dependence of resonance field (Hr) 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 (4πMS), 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)×10⁻⁷ to 5.0(5)×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.