XAFS study of Zr site preference for Nd16Fe75.5Zr0.5B8 in disproportionated, partially/fully recombined states of HDDR process

Abstract X-ray absorption fine structure (XAFS) measurements were done for the Zr K-edge of Nd 16 Fe 75.5 Zr 0.5 B 8 magnets in the disproportionated, partially and fully recombined states of HDDR process. XAFS results reveal that Zr preferentially occupies Fe(j 2 ) and Fe(j 1 ) sites in the Nd 2 Fe 14 B structure for the disproportionated, partially and fully recombined states. The partially recombined sample shows larger magnetic anisotropy but a smaller coercivity than the fully recombined one. Fourier analyses of the XAFS results show the rearrangement of Zr atoms as the HDDR process proceeds; some Zr at Fe(j 1 ) sites move to Fe(j 2 ) sites in the partially recombined state but they turn back to Fe(j 1 ) sites in the fully recombined state. The interchange of preferential site occupancy of Zr between Fe(j 1 ) and Fe(j 2 ) sites with proceeding recombination may be responsible for the degree of magnetic anisotropy.