Ferromagnetic Resonance in Manganese Ferrite Single Crystals

The microwave properties of two types of manganese ferrite single crystals have been investigated by means of the ferromagnetic resonance phenomenon from 300°K to 4.2°K and at 24 000, 9100, 5600, and 2800 Mc/sec. The low resistivity of one of the crystals, believed to be related to the presence of divalent iron, led to significantly different microwave behavior. Resonance lines as narrow as 47 oe have been obtained; however the width depends markedly on crystal direction, temperature and microwave frequency. The $g$-values are close to 2.00 under all conditions. The anisotropy, although frequency insensitive, increases rapidly at low temperatures. The Kramers-Krönig relations between absorption and dispersion are satisfied, and the line shape is roughly Lorentzian. Double resonances have been observed, and it is speculated that this may be a general phenomenon in single-crystal ferrites under suitable conditions.