Thickness dependent structural, magnetic and magneto-dynamic properties of Mn rich Ni-Mn-Sn films

Off-stoichiometric Mn-rich Ni-Mn-Sn films of different thicknesses were deposited on Si (100) substrate by dc magnetron sputtering at ambient temperature and then annealed ex situ at 550 °C for 1 h under high vacuum. X-ray diffraction patterns revealed that as deposited films were amorphous, whereas the annealed films exhibited room temperature cubic structure with space group Fm3¯m (space group 225) with high degree of L21 ordering. Magnetic study of the annealed film disclosed room temperature ferromagnetic order with easy axis of magnetization along the plane of the film. Magneto-dynamic study of the annealed films was carried out using a micro strip-ferromagnetic resonance (FMR) spectrometer. The deduced values of saturation magnetization from frequency dependence of the resonance field of the FMR spectra were in close agreement with those obtained from dc magnetization measurement. The analysis of frequency variation of linewidth shows the presence of low Gilbert damping constant of 0.007 for the 500 nm thick film. Gilbert damping constant was found to increase slightly with film thickness. The polar angle variation FMR study for 1500 nm film revealed the presence of high effective perpendicular anisotropy (K1 ≈ −9.0 ± 0.5 × 105 erg/cm3) and easy magnetization along its plane.