Perpendicular Standing Spin Wave and Magnetic Anisotropic Study on Amorphous FeTaC Films

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 the microstrip 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 the first perpendicular standing SW (PSSW) mode (n = 1), especially for d = 50, 100, and 200 nm films. The angular (φ
_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 4πM
_S
, uniaxial anisotropic constant (K
_u
), g-factor, and exchange stiffness constants (A
_ex
), are estimated for different FeTaC film thicknesses. A
_ex
is found to increase from 2.00(4)×10
^-7
to 3.50(5)×10
^-7
erg/cm as the thickness of film increases from 50 to 200 nm, respectively, due to a surface pinning effect or significant inhomogeneity, especially at higher thickness films.