STRUCTURE AND MAGNETISM OF FCC PD-MN ALLOYS

To understand the relationship between the structure and magnetism of fcc Pd-Mn spin-glass disordered alloys, we have measured the lattice p arameters, electron diffraction (ED) patterns, x-ray diffuse scatterin g intensity, and magnetic susceptibilities. The lattice parameters of the Pd1-xMnx alloys show a nonlinear increase with composition for 0 l ess-than-or-equal-to x less-than-or-equal-to 0. 25. Peculiar diffuse s cattering has been observed at the 100, 110, and the equivalent positi ons on ED patterns in the composition range from x = 0.15 to 0.25. War ren-Cowley short-range order (SRO) parameters from a single crystal of the x = 0.25 alloy were obtained by analyzing the x-ray diffuse inten sity. Extra diffuse maxima were observed at 1/2, 1/2, 1/2 and equivale nt positions, in addition to the diffuse scattering described above, a nd their intensity is 20% of that at the 100 position. A correlation l ength has been deduced to be about 10 angstrom from estimating the rec onstructed diffuse intensity distribution using the SRO parameters det ermined experimentally. A magnetic phase diagram has been constructed from measuring the freezing temperature (T(g)). T(g) shows a peculiar dependence for a Mn content below x = 0.05, above which it increases m onotonically up to x = 0.17, and then rises dramatically up to x = 0.2 5. The paramagnetic Curie temperature (THETA) is negative for all the compositions, which indicates that the antiferromagnetic interactions are influential. Ordered-structure experiments indicate that the value s of T(c) are very low for alloy compositions of x < 0.244.