ANOMALOUS MAGNETIC DISACCOMMODATION IN YTTRIUM-IRON-GARNET

An alternative approach to account for the oxygen loss at sintering te mperatures in YIG allows an explanation to the not yet elucidated acco mmodation effect observed in the magnetic disaccommodation spectrum of nominal stoichiometric samples below 130 K; i.e., the observed time i ncrease of the initial permeability mu, after demagnetizing the sample s instead of the usual time decrease. In single phased YIG samples sin tered under low oxygen pressures, electric balance considerations lead s 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 mu(i ) smaller than of the sample free of interstitials. However, given a s uitable energy of activation at a given temperature, the potential ene rgy barriers would be surmounted and the interstitial magnetic moments would become more or less arranged into the ferromagnetic order, atta ining a minimum of free energy. Thus, the impediments to domain wall f ormation and movement would be at least partially eliminated, causing the observed accommodation outcome. (C) 1998 Elsevier Science B.V.