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.
Categories: cond-mat.mes-hall cond-mat.mtrl-sci