The Importance of Vacancies and Interstitial Atoms in the Development of Induced Anisotropy

Experimental data on the annealing of thin permalloy films in a magnetic field parallel to the axis of anisotropy are presented. The films are obtained by vacuum evaporation at the rate of 40 Å/s on glass substrates heated from room temperature to 200 °C. The shape of the isotherms of the anisotropy field (H K ) depends upon the temperature of the substrate in various ways: 1) H K increases with annealing time up to saturation, 2) H K passes through a minimum, 3) H K decreases to a definite value. A quantitative description of the effects observed is given in terms of vacancy ordering and annihilation of vacancies and interstitials. The activation energies of these processes are calculated.