Magnetic Resonance in the Spiral Phase of Polycrystalline MnAu₂ at 20–26 GHz

Abstract

Microwave absorption has been studied at 20–26 GHz in polycrystalline MnAu₂ over a temperature range of 5–440 K and in magnetic fields up to 20 kOe. MnAu₂ has planar spiral magnetic ordering below a Néel temperature of T_N=363 K. Paramagnetic resonances was observed above T_N. Although theory predicts no low frequency resonance in the spiral magnetic phase below T_N, two distinct absorption peaks were observed and studied as functions of frequency, polarization, magnetic field, and temperature. One set of resonances is consistent with paramagnetic resonance of a postulated disordered spin component in the spiral phase of MnAu₂. Possible explanations for the second resonance are discussed. A possible resonance in the fieldinduced fan phase of MnAu₂ was also observed.