Molecular field coefficients and cation distribution of substituted yttrium iron garnets

摘要

The saturation magnetizationMs(T) of Ga, Al, Sc, and CaVBi substituted Y3Fe5O12(YIG) single crystals and of polycrystalline Ca/Ge and Ca/Ti substituted YIG has been investigated for 4.2 K les;Tles;TC. The samples were repeatedly annealed and quenched at different equilibrium temperatures 773 Kles;Teles;1523 K. The attained site exchange of Fe and the substituents between theaanddsites resulted in considerable changes ofMs(T). From a fit of the Neacute;el molecular field theory to theMs(T) data the dependence of the magnetic moments atT= 0 K and of the molecular field coefficients on the amount of nonmagnetic substitutions on theaanddsites were determined. It turned out that ionhyphen;specific sets of equations are required accounting for the rsquo;rsquo;particular ion effectrsquo;rsquo; of different cation species. The cation distributions inferred from the magnetic data have been analyzed along with a thermodynamic equilibrium model. The derived site stabilizing energies for the mixed Fendash;Ga and Fendash;Al garnets agree well with recently reported data. New results are presented for the site stabilizing energies in Ca/Ge:YIG and for the substituents Sc and Ti with octahedral site preference.