Anomalous magnetic disaccommodation in yttrium iron garnet

Abstract

An alternative approach to account for the oxygen loss at sintering temperatures in YIG allows an explanation to the not yet elucidated accommodation effect observed in the magnetic disaccommodation spectrum of nominal stoichiometric samples below 130 K; i.e., the observed time increase of the initial permeability μi after demagnetizing the samples instead of the usual time decrease. In single phased YIG samples sintered under low oxygen pressures, electric balance considerations leads to the existence of interstitial cations. These cations are expected to affect the normal superexchange interactions and the ferromagnetic ordering, obstructing the formation and movement of the domain walls after the sample has been demagnetized; the net effect would be a μi smaller than that of the sample free of interstitials. However, given a suitable energy of activation at a given temperature, the potential energy barriers would be surmounted and the interstitial magnetic moments would become more or less arranged into the ferromagnetic order, attaining a minimum of free energy. Thus, the impediments to domain wall formation and movement would be at least partially eliminated, causing the observed accommodation outcome.