Soft Magnetic Properties of Fe-N Films Composed of Two Phases

Abstract

Fe-N films were synthesized by means of ion beam deposition. Nitridation was performed using an assist gun during the sputtering of Fe films. The as-deposited Fe-N films consisted of two phases, μ-Fe and γ'-Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> N, and had a high coercive force H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> of over 20 Oe. When the films were annealed in vacuum, their H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> improved drastically, and had a minimum value of less than 1 Oe at 400°C. The films also had a high permeability of over 2000 as well as high resistivity (around 80 μΩ-cm), in spite of a high saturation magnetization (around 18 kG). The small grain size and stress relaxation in the films are closely related to the soft magnetic properties. The volume fraction of the γ'-Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> N phase also affected the decrease in H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , because the anisotropy normal to the film plane is reduced by increasing the magnetostatic energy when the volume fraction was 0.5.