Influence of excess N on FeZrN soft magnetic film

Abstract

The soft magnetic properties of the FeZrN ternary system were studied in association with excess nitrogen (N) in films. The proportion of excess N (EN) is defined (z−y)/[x+(z−y)]×100 for the film composition expressed FexZryNz. This is because the advent of soft magnetism, in this system, is assumed to be due to suppression of grain growth of α-Fe by ZrN precipitated in grain boundaries, thus causing a ‘‘nanocrystalline effect.’’ This means that N exceeding the amount of Zr is considered ‘‘excess.’’ This paper presents the influence of excess N on soft magnetic properties, and the following conclusion was obtained. Excess N first formed a supersaturated solid solution with Fe, and acted as the origin of induced magnetic anisotropy. Supersaturated N easily moved in Fe and the orientation of easy axis was reversibly changed by re-annealing at 150 °C in a magnetic field perpendicular to the easy axis. When N was in excess, some part of excess N formed Fe4N. Fe4N caused a dispersion of the microscopic anisotropy, and lowered the permeability of the macroscopic hard axis. Both supersaturated N and Fe4N increased magnetostriction constants.