Anisotropy in the Antiferromagnetic MnF2

Abstract

The major part of the anisotropy in the paramagnetic susceptibility of Mn${\mathrm{F}}_2$ above the Curie point, as measured by Stout and Griffel, can be accounted for by magnetic dipole interactions. These interactions affect the anisotropy in different ways above and below the Curie point and lead to an anisotropy field of the order of 8800 oersteds at O°K. Other sources of anisotropy in antiferromagnetics are discussed, in particular that due to crystalline fields which is also present in magnetically dilute paramagnetic salts. The anisotropy field below the Curie point can be measured by antiferromagnetic resonance. It is predicted that this will require wavelengths of 1 mm at 0°K increasing to perhaps 2 mm at $0.9T_c$. Or one may use centimeter waves and static fields of 1.0×${10}^5$ oersteds at 0°K increasing to perhaps 1.7×${10}^5$ oersteds at $0.9T_c$.