Crystallographic and magnetic properties of NdFe(10.7)TiM(0.3)(M=B,Ti)

NdFe(10.7)TiM(0.3)(M=B, Ti) has been studies with x-ray diffraction, Mossbauer spectroscopy, and a vibrating sample magnetometer. The alloys were prepared by arc-melting under an argon atmosphere. The NdFe10.7TiB0.3 exhibits a pure single phase, whereas the NdFe10.7Ti1.3 contains some alpha-Fe, from x-ray and Mossbauer measurements. The NdFe10.7TiB0.3 has the ThMn12-type tetragonal structure with a(0)=8.587 Angstrom and c(0)=4.788 Angstrom. The Curie temperature (T-C) is 570 K from Mossbauer spectroscopy performed at various temperatures ranging from 13 to 770 K. Each spectrum below T-C was fitted with five subspectra of Fe sites in the structure (8i(1), 8i(2), 8j(1), 8j(2), and 8f). The area fraction of the subspectra at room temperature are 16.4%, 8.2%, 14.8%, 21.3%, and 39.3%, respectively. Magnetic hyperfine fields for the Fe sites decrease on the order of H-hf(8i)>H-hf(8j)>H-hf(8f). The average hyperfine field H(h)f(T) of the NdFe10.7TiB0.3 shows a temperature dependence of [H-hf(T)-H-hf(O)]/H-hf(O)=-0.39(T/T-C)(3/2)-0.17(T/T-C)(5/2) for T/T-C<0.7, indicative of spin-wave excitation. annealing the alloy at around T-C for 60 min resulted in a two phase microstructure consisting of a ThMn12-type structure and alpha-Fe. (C) 1996 American Institute of Physics.