XANES study on NdFeB alloys with refractory Titanium addition

D.DEREWNICKA; LEDE E.; M.R. PAGNOLA; L. G. PAMPILLO; F. D. SACCONE

Sao Carlos

Conferencia; NANOMAT 2012, The 5th Latin American Conference on Metastable and Nanostructured Materials; 2012

UFSCar , UNICAMP

Rapidly quenched ribbons of nominal composition NdyFe(86-x-y)B14Ti x (x = 0, 2, 4; y = 7, 8) were annealed at 953K for 20 minutes. Their magnetic properties were measured using a vibrating sample magnetometer, Nd8Fe74B14Ti4 alloy showed the best ones. The crystalline and electronic structures were investigated by high-resolution transmission electron microscopy (HR-TEM), Mössbauer spectroscopy (MS) and X-Ray Absorption Near Edge Structure (XANES). XANES experiments were performed to measure the spectra of Nd-LIII, Fe-K and Ti-K edges. The analysis of the most relevant characteristics of each spectrum revealed that in samples without Ti there is a charge transfer from Nd to Fe while Nd concentration increase from 7 to 8 %. Furthermore, as Ti is added, there was a distinct behaviour from samples with Nd 7% respecting to Nd 8%. For example, the former showed that the density of empty states increases in Nd and decreases in Fe, whereas the opposite occurs in the latter case, provided with the addition of Ti 4%. This phenomenon might explain the remanence and coercivity reinforcement whenever improving magnetic properties is caused by a reduction of grain size in the alloys, as well as the ratio and distribution of magnetically soft and hard phases, as well as a different magnetic moment per atom, as a consequence of modification of their electronic band structures.