Soft Magnetic Properties of Fe-Ni-Nb Alloy Films

The relation between the soft magnetic properties and local anisotropy fluctuation measured by the dynamic differential susceptibility method in Fe-Ni-Nb alloy films was clarified and discussed in comparison with Fe-Si-Al alloy films. Fe-Ni-Nb alloy films with excellent soft magnetic properties, 5 MHz values of μ_eff = 6500 for 1000 Å thick films were obtained. For Fe-Si-Al alloy films, the magnitude of μ_eff = 6500 is proportional to 1/S² (where S is a structure constant) and independent of the value of H_k, while for Fe-Ni-Nb alloy films, the value of S is about one-tenth of that in Fe-Si-Al alloy films, and the magnitude of μ_eff 6500 does not depend on S. Rather, this magnitude is dependent on the value of H_k, and is almost equal to 4πM_s/H_k, obtained from a rotational magnetization model in a uniaxial single-domain particle.