Inverse giant magnetoresistance in granular Nd/sub 2/Fe/sub 14/B//spl alpha/-Fe

Partially amorphous Nd-Fe-B ribbons containing 20 or 50 wt% Fe in excess of the nominal composition Nd/sub 2/Fe/sub 14/B with 2.9 wt% Cu and 9.7 wt% Zr (referred to Nd/sub 2/Fe/sub 14/B) were prepared by melt-spinning. After a heat treatment the material consists of a mixture of three parts: hard magnetic grains of the Nd/sub 2/Fe/sub 14/B phase with /spl alpha/-Fe grains and, in the case of 20 wt% excess Fe, small amounts of a metastable cubic phase, Nd/sub 2/Fe/sub 23/B/sub 3/. Samples with 20 wt% Fe show a superposition of anisotropic magnetoresistance and giant magnetoresistance (GMR) effects, depending on structural changes caused by heat treatments at various annealing temperatures. For measurements with the applied field both parallel and perpendicular to the sample current an isotropic positive magnetoresistance ratio, MR=[R(H)-R(0)]/R(0), called inverse GMR has been found for samples with 50 wt% excess Fe.