Dependence of Ferromagnetic Resonance Linewidth on Structural Defects in Single Crystals of Lithium Ferrite

Abstract

Submicroscopic defects have been established as the major cause of linewidth in lithium ferrite single crystals. Over 100 highly polished lithium ferrite spheres showing no microscopic defects exhibited ΔH's ranging from 2 to 60 Oe. Spheres of low ΔH and high ΔH were chemically polished and etched. Low ΔH spheres had very few pits; high ΔH spheres were severely mottled and etched. X‐ray topography and etching of (111) plates have confirmed that regions with defects >10⁵ cm⁻² exist near regions of only 10² cm⁻². The regions are often separated by a sharp boundary along 〈110〉. Spheres prepared from very low‐pit‐count material repeatedly had ΔH's of heat treatment. The defects appear to be dislocations and compositional variations. Heat treatment at 850°C caused no observable change in x‐ray topographs. By careful selection of the crystals of low defect content, ΔH's as low as 0.87 Oe at 5.1 GHz and 25°C have been observed.