Domain wall freezing and magnetic viscosity in helical antiferromagnet

Abstract

Domain wall dynamics in antiferromagnets is of a paramount importance in designing functional materials for spintronics and data storage applications, and its studying is a challenging experimental task. We present simple and accessible ways to track domain wall fluctuations and freezing in helical antiferromagnets, both considering the existence of intrinsic magnetic moments of Hubert domain walls. Two different techniques—dynamic measurements of reversible inverse magnetostriction and measurements of static magnetic susceptibility—delineated the same temperature range of domain wall freezing in the dysprosium single crystal. The main experimental protocol in dynamic measurements was the relaxation of reversible inverse magnetostriction upon switching off applied magnetic field, like the procedure used in studying magnetic viscosity. These experiments, apart from revealing domain wall freezing, enabled us to clarify the role of domain walls and lattice contributions in the anomaly of magnetoelastic coupling just below the Néel point. Furthermore, beyond the temperature range of domain wall freezing, the kinetics of relaxation of reversible inverse magnetostriction and temperature dependence of magnetic viscosity in antiferromagnetic dysprosium agree with the classical Néel model of the thermal fluctuation magnetic aftereffect.