Do thermal fluctuations influence the recoil loops of nanocomposite magnets?

Abstract

An exchange-coupled FePt/Fe3Pt nanocomposite system with well defined hard/soft two-phase morphology was prepared by reducing chemically synthesized FePt/Fe3O4 bimagnetic nanoparticles. It was interesting to observe that the recoil loop openness is strongly dependent on the sweep rate of applied fields. A quantitative analysis shows a linear relation between the openness of recoil loops and the reciprocal activation volume, indicating that the recoil loops are intimately related to thermal fluctuation. The large open area of the recoil loops for nanocomposite magnets compared to that of single phase magnets is attributed to the unstable magnetic moments in the soft phase.