Relaxation in the ferromagnetic phase of terbium arsenate (TbAsO₄)

Abstract

Below !i"c = 1.5 I< TbAsO, is an Ising ferromagnet with induced magnetic moments. A superstructure of the magnetic moments found by Schafer and Will may be explained by very small ferromagnetic domains. A simple estimation of the free energy a t ! l ' = 0 yields 0.05 pm for the thickness of these domains. In the ordered phase the complex magnetic ac susceptibility is strongly frequency dependent. The relaxation depends on two coupled processes. It is assumed that the process at lower frequencies is due to domain wall shifting and the process at higher frequencies is caused by the internal field. The frequency dependence can be described by an extension of the Debye equation which decouples the two processes. The susceptibility of a system with rigid domain walls is determined in mean field approximation.

Dilution-Induced Slow Magnetic Relaxation and Anomalous Hysteresis in Trigonal Prismatic Dysprosium(III) and Uranium(III) Complexes

“…Only the faster relaxation at high frequencies in 3 , which becomes dominant upon dilution of the spins, may be ascribed to a molecular process. Analogies for this slower process can be drawn from paramagnetic relaxation studies performed on the compounds Ln(OH) 3 (Ln = Tb, Dy, Ho), dysprosium ethyl sulfate (Dy(CH 3 CH 2 SO 4 ) 3 ·9H 2 O, DyEtS), and terbium arsonate starting in the 1960s. In these systems, two relaxation domains are also apparent at low temperatures, albeit on a much faster time scale.…”