Frequency Dependence of Magnetic Resonance inα-Fe2O3

Magnetic resonance absorption in single crystals of natural $\alpha$-${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$ was examined in the wavelength range from 5.4 mm to 6.2 cm. Resonance fields $H_r$ observed in the basal plane do not give a quadratic relation with the normal resonance field $H_0$ as predicted by the usual Kittel formula, but rather the following linear relationship: $\frac{h\nu }{g\beta }=H_0=H_r+H_A$, where $H_A$ is ${4.2}_{5}K$ oe and $g$ is ${2.5}_4$.