Antiferromagnetic Resonance

The frequencies at which electronic resonance will occur apparently lie beyond the region now available with conventional microwave equipment for those materials having Curie temperatures well above 0°K. ${\mathrm{Cr}}_2$ ${\mathrm{O}}_3$, MnO, MnTe, and MnSe show a large decrease in the amount of resonance absorption as the material (powdered) is lowered through its Curie temperature, with only a small residual absorption remaining in the antiferromagnetic region. MnSe has an absorption vs temperature hysteresis loop that is correlated with a magnetic susceptibility loop previously reported for this material. The $g$ values remain constant as the absorption decreases. Considerable absorption is found at zero static magnetic field for MnO, MnS, and MnTe. The line widths increase sharply as the temperature of the material approaches the Curie temperature. CoO and V${\mathrm{O}}_2$ give no detectable absorption either above or below their Curie temperatures. NiO and CuO show no absorption in the antiferromagnetic region.