Effect of Low-Temperature Magnetic Anneal on the Linewidth of Garnets Containing Fe2+ Ions

Publisher Website
Google Scholar
Abstract
The linewidth of garnets containing Fe2+ ions was measured from 4.2° to 400°K at 10 and 25 kMc/sec for unannealed samples and samples annealed in the three major crystallographic axes. It was found that the linewidth at low temperatures depends very strongly on the magnetic history of the sample during the cooling cycle. For samples cooled in zero magnetic field, the linewidth at 4.2°K becomes very large and resembles the case of nonsaturated resonance where domains go through resonance at different fields. Magnetization measurements of such samples at 4.2°K confirm qualitatively the increase of field for saturation. The linewidth of samples cooled in a magnetic field is much smaller and exhibits the characteristic peak as a function of temperature. The wellknown electron diffusion at low temperatures, which causes induced anisotropy in these samples, affects both the value and position of the peak. In particular, the linewidth is reduced and the peak is shifted to higher temperatures when the sample is cooled and measured in the same direction. Any change of the direction of the applied magnetic field increases the linewidth and shifts the peak to lower temperatures. Above 100°K this effect disappears. This is in good agreement with induced anisotropy measurements which show that above this temperature the diffusion time constant of the electrons is too short to affect the linewidth. We conclude that at low temperatures electron diffusion affects the linewidth but is not the main relaxation mechanism. The latter seems to be intraionic relaxation.

This publication has 2 references indexed in Scilit: