Microwave Resonance and Relaxation of Manganese Iron Ferrites

Abstract

Microwave resonance measurements are reported at 16.85 Gc/sec in the temperature range 1.5° to 300°K for single crystals of composition MnxFe3−xO4 with x = 1.318, 1.007, and 0.990. For x = 1.318, the linewidth and the g factor, if this is calculated in the usual way, both pass through maxima as a function of temperature. These effects are compared to the predictions of a slow relaxation model, and indicate a splitting of a low-lying pair of energy levels of about 7.5 cm−1, and relaxation times across these levels of about 10−11 sec. The specimens close to manganese ferrite also show these relaxation effects but on a much reduced scale. They give splittings and relaxation times similar to those above. Sharp peaks in the linewidth as a function of orientation were found at [110] directions at 4.2°K and below, and were similarly dependent on composition. It is suggested that the slow relaxation is associated with manganese ions of some sort.