STRUCTURE AND MAGNETIC-PROPERTIES OF ND6FE13CU

A new phase delta in the ternary system Nd-Fe-Cu is identified as Nd6F e13Cu. X-ray powder diffraction patterns of a sample annealed at 540-d egrees-C for 1000 h are indexed on a tetragonal unit cell with a = 8.0 9 angstrom and c = 22.26 angstrom. The Curie temperature T(c) is 190 /- 5-degrees-C and the small net magnetization at 4.2 K of 18 mT (2 J T-1 kg-1) after correcting for the presence of 1.5% Nd2Fe17 suggests a ferrimagnetic spin structure. There is a spin rearrangement in a fiel d of 1.5 T at 4.2 K and a metamagnetic transition is also observed on hydrogenation. Mossbauer spectra at 15 K are fitted with four subspect ra with hyperfine fields of 36.9, 33.2, 30.6, and 23.0 T. X-ray measur ements on oriented powder indicate that the easy direction of the net magnetization lies along the c axis, but Mossbauer spectra show that n one of iron sublattices have their magnetization aligned along c.