Effect of the grain size on the magnetic properties of nanophase REFeB alloys

Abstract The dependence of the remanence Jr and intrinsic coercivity iHc on the grain size dg for nanocrystalline RE (Nd–Pr)–Fe–B melt spun alloy ribbons was studied for single-phase stoichiometric 12% RE alloys and for nanocomposite Fe-rich 8% and 10% RE alloys. For single-phase alloys, iHc decreases as the grain size diminishes, whereas for the two-phase nanocomposite alloys two different trends were observed: a rather constant dependency with decreasing dg for 10% RE alloys (with 15% soft phase volume fraction) and an increasing trend for 8% RE alloys (with 30% soft phase volume fraction). The results are broadly in agreement with the predictions of micromagnetic modelling.