Uniaxial-Anisotropy Spectrum in Nonmagnetostrictive Permalloy Films

Abstract

The uniaxial‐anisotropy spectrum in Permalloy films has been studied by: (1) deposition in H_∥ on a substrate at temperature T_s, (2) annealing in either a dc field H_⊥ or a circular rotating field H_r for specified time intervals, (3) quenching of the substrate holder by water‐cooled coils. Significant aspects of this procedure are: (1) annealing is carried out before exposure to air (oxygen), (2) quenching gives well‐defined annealing times, (3) each experiment involves freshly deposited samples which are in a well‐defined and reproducible state. These experiments have led to the identification of five separate contributions to the anisotropy in nonmagnetostrictive Permalloy, namely: (1) and (2) two types of contributions due to lattice vacancies with rotational activation energies≤0.2 eV and which became locked after exposure to air (oxygen), (3) and (4) two contributions with rotational activation energies∼1 eV, thought to be due to half self‐interstitials and carbon interstitials, respectively, and (5) directed Fe–Fe pairs.