The magnetization process and coercivity in random anisotropy systems

Abstract

A numerical simulation of a two-dimensional XY model has been carried out to study the thermal behaviour of the magnetization process and the variation of the coercive field as a function of the random anisotropy amplitude. The existence of two different magnetic regimes is evidenced: a low-anisotropy regime, which is characterized at zero temperature by a power law increase of the coercive field as the anisotropy amplitude increases, and a regime for anisotropy values higher than D/zJ=0.5, for which the system behaves as an assembly of quasi-independent clusters of two or three atoms. In this regime, the coercive field increases linearly with the anisotropy strength. The numerical estimates of the power law exponent are in good agreement with the heuristic predictions of Imry and Ma (1975). The domain wall motion and the spin configuration for the two anisotropy regimes have also been studied, pointing out the differences in the pinning process between both regimes. The thermal dependence of the coercive field has been obtained and fitted to an exponential law.

Ferromagnetism inCo7(TeO3)4Br6Prester1, Živković2, Zaharko3 et al. 2009Phys. Rev. B2160View full textAdd to dashboardCite

“…has been found to describe well the behavior of many nanostructured magnetic systems, like thin magnetic films 17 and amorphous systems 19,20,21,22 . The common feature in those systems was the presence of magnetic clusters with the well defined anisotropy barrier, where jumps of magnetic moments of the clusters over the barriers are temperature assisted.…”

Field-induced magnetic phase transitions and metastable states in Tb3Ni

“…, where V t represents the degree of easiness for thermally activated movement of domain walls, was used for modeling of a thermally activated domain walls displacement in ferromagnets with a high uniaxial anisotropy [52][53][54]. The exponential decay of the coercive field following an empirical formula H C (T )/H C (0) = exp(−αT ) is typically observed in a numerous amorphous systems where random magnetic anisotropy plays a crucial role [55]. The effect of averaging in amorphous materials results in a faster decrease in the anisotropy constant K ave with temperature and thus in a faster decrease in H C than in crystalline materials [56].…”

Application of the Stoner–Wohlfarth model with interaction for the determination of the saturation magnetisation, anisotropy field, and mean field interaction in bulk amorphous ferromagnets

“…The origin of the coercivity is local irregularities in the magnetisation arising from local anisotropy. Ribas et al [45] in the context of random anisotropy systems explore the thermal behaviour of the coercive field using numerical simulations. At finite temperatures thermal activation to overcome energy barriers is key to magnetisation reversal.…”