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 parameters, electron diffraction (ED) patterns, x-ray diffuse scattering intensity, and magnetic susceptibilities. The lattice parameters of the ${\mathrm{Pd}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$ alloys show a nonlinear increase with composition for 0≤x≤0.25. Peculiar diffuse scattering has been observed at the 100, 110, and the equivalent positions on ED patterns in the composition range from x=0.15 to 0.25. Warren-Cowley short-range order (SRO) parameters from a single crystal of the x=0.25 alloy were obtained by analyzing the x-ray diffuse intensity. Extra diffuse maxima were observed at 1/2,1/2,1/2 and equivalent positions, in addition to the diffuse scattering described above, and their intensity is 20% of that at the 100 position. A correlation length has been deduced to be about 10 Å from estimating the reconstructed diffuse intensity distribution using the SRO parameters determined experimentally. A magnetic phase diagram has been constructed from measuring the freezing temperature (${\mathit{T}}_{\mathit{g}}$). ${\mathit{T}}_{\mathit{g}}$ shows a peculiar dependence for a Mn content below x=0.05, above which it increases monotonically up to x=0.17, and then rises dramatically up to x=0.25. The paramagnetic Curie temperature (FTHETA) is negative for all the compositions, which indicates that the antiferromagnetic interactions are influential. Ordered-structure experiments indicate that the values of ${\mathit{T}}_{\mathit{c}}$ are very low for alloy compositions of x<0.244.