Magnetic domains and demagnetizing fields in FeTb thin films

Abstract

The magnetic properties of 500 Å thick amorphous thin films with 0.16 < x < 0.35 have been studied experimentally. All films possess a strong perpendicular magnetic anisotropy (PMA) with an anisotropy constant . Using a polar Kerr microscope, the magnetic domain patterns in the samples with different values of the compositional parameter x were observed, revealing strong correlations between the domain shapes and the magnetic parameters of the films. In order to explain the experimental observations a micromagnetic model of domain growth on a two-dimensional hexagonal grid is developed. By means of an FFT algorithm with periodic boundary conditions an adequate description of the demagnetizing field distribution was achieved. The model allows us to calculate both the domain patterns and the hysteresis loops, showing good agreement with the experimental observations. Both the experimental and the theoretical studies demonstrate that the closeness to the compensation point is the decisive factor controlling the micromagnetic behaviour of the films.