Low-Temperature Antiferromagnetic Resonance in αFe2O3

Abstract

Antiferromagnetic resonance (AFMR) at 35, 70, and 121 Gc/sec in single‐crystal synthetic and natural αFe₂O₃ from 4.2° to 280°K has been observed. The usual low‐field AFMR as well as the spin‐flop resonance mode are observed with pulsed magnetic fields applied parallel to the c axis. The data extend from well below the spin reorientation transition temperature T_M (about −10°C) to well above T_M. The spin‐flop mode joins smoothly with the canted high‐frequency mode above T_M. The usual AFMR terminates abruptly at T_M. The three modes observed here for the first time in αFe₂O₃ require either high fields or high frequencies or both for observation. The effects of the Dzyaloshinsky‐Moriya field H_DM on the spin‐flop resonance, the usual AFMR, as well as possible effects of spontaneous sublattice magnetizations are discussed.