Measurements on Lithium Ferrite Crystals having Near-Zero Defect Concentrations

From a batch of lithium‐rich highly ordered single crystals of lithium ferrite, a group of 13 spheres were prepared using regions selected for low defect concentrations. Linewidths measured at 5.1 GHz and ∼300°K ranged from 0.87 to 2.06 Oe with a mean value of 1.35 Oe. The resistivity of the crystals was 3 Ω·cm and ${\text{4πM}}_s$ was $\text{3720±50\hspace{0.17em}}\mathrm{G}$ . The narrow linewidths in the presence of such high conductivity suggests a conductivity mechanism other than the usual one involving Fe²⁺ ions. The sphere with the lowest $\mathrm{\Delta H}$ was used to measure the temperature dependence of $\mathrm{\Delta H}$ , ${\mathrm{\Delta H}}_{\text{k→0}}$ and $H^A\text{[111]}$ between 4.2° and 300°K at 10.4 GHz. The $\mathrm{\Delta H}$ ranged from 1.45 Oe at 300°K to 0.55 Oe at 4.2°K with a peak of 2 Oe near 30°K. At 250°K, ${\mathrm{\Delta H}}_{\text{k→0}}$ was 0.4 Oe. It exhibited a peak near 30°K (whose maximum was not measured) and was only 0.06 Oe at 4.2°K. The anisotropy field $H^A\text{[111]}$ decreased monotonically from 625 G at 4.2°K to 390 G at 300°K. The possession of samples having very small linewidths permitted the study of the effect of ordering on the room‐temperature linewidth uncomplicated by other effects.