Kinetics for changes in anisotropy, coercivity, and argon content of transition metal-rare earth films

• Published in: Journal of applied physics 1985-01, Vol.57 (8), p.3592-3594
• Main Author: LUBORSKY, F. E
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Other techniques and industries
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.335016

Amorphous films of transition metal-rare earth alloys were prepared by rf bias sputtering ∼1000 Å thick, and were protected with ∼1000-Å SiO2, under conditions to provide an easy axis perpendicular to the film plane. Some of the kinetics of the changes in the parameters affecting the domain size were measured, namely the anisotropy, the coercivity Hc and the argon content. Both isothermal and isochronal exposures were used. The decrease in the perpendicular anisotropy K⊥ and Hc and the increase in the planar anisotropy all follow first-order kinetics, that is, the Johnson–Mehl–Avrami exponent n=1.0. The activation energy for the change in K⊥ was 1.0±0.2 eV. The changes in anisotropy were the rate limiting factor in the lifetime of the films. The Hc decreased with ΔE=0.6±0.2 eV while the Ar content decreased with ΔE=0.08±0.05 eV. Because of the large difference in activation energy for the change in Ar compared to the changes in K or Hc we conclude that the rate limiting step for the change in Ar is different than the rate limiting step for the changes in K and Hc. At least two mechanisms have been associated with the changes on annealing. One is the oxidation of the rare earth component even through the SiO2 overlayer; the other is the release of Ar which changes the local stress in the film or changes the degree of isolation of the columnar structure by the Ar.