Structural and magnetic effects of nitrogen addition in Fe-Ni invar films

초록

The microstructure and magnetic properties of Fe-Ni-N/Cu films, prepared by the DC magnetron sputtering method, with different thicknesses of Fe-Ni-N have been studied by the methods of X-ray diffraction (XRD), Ellipsometry, Brillouin light scattering (BLS), and magnetization measurements. It has been found that the optical absorption strength for the Fe-Ni-N film was reduced significantly at low energies (< 3 eV) [1]. Also, the dielectric functions indicate that the electrical conductivity of Fe-Ni-N was reduced significantly compared to that of Fe3Ni. The thickness dependence of magnetization can be explained by means of the Klein and Smith theory [2]. Collective spin waves in Fe-Ni-N films of 40 and 30 nm in thickness have been studied by means of BLS at room temperature in applied magnetic field of up to 1.0 kG [3]. From BLS the values of the spin wave stiffness constant were determined to be D = 73.9 and 86.7 meV2 for film with thickness of 30 and 40 nm, respectively. These values are in good agreement with the value obtained from the temperature dependence of magnetization. In order to confirm the magnetic effects of nitrogen on the Fe-Ni-N films we have investigated the Nels prediction for the wall motion coercivity mechanism [4] and the wall pinning based on Gaunts strong pinning theory [5]. On the basis of the experimental results, the microstructure and magnetic properties of the Fe-Ni-N films have been discussed in terms of the thickness dependence and the dielectric property has been compared with that of Fe-Ni invar films.