Diffuse scattering intensity near the Bragg reflection in a (para)magnetic bulk face-centred cubic Ni3Fe-type permalloy

Within the scope of the self-consistent-field (SCF) and mean-SCF approximations, the Matsubara-Kanzaki-Krivoglaz lattice-statics method as well as the Krivoglaz-Clapp-Moss approach, the kinematic diffuse scattering intensities near the Bragg reflection caused by the atomic short-range order (taking into account the long-range magnetic order) in a (para) magnetic bulk face-centred cubic Ni-Fe alloy are investigated in detail. The reciprocal-space symmetry analysis of both the 'direct' 'electrochemical' and short-range 'exchange' interactions as well as the long-range 'indirect' 'strain-induced' contribution to the Fourier components of interatomic 'mixing' energies and the diffuse scattering intensity contributions near the 'fundamental' Gamma(000)-point is carried out. In the Gamma-point vicinity, the rigorous symmetry regularities for all the energy and diffuse scattering intensity contributions are formulated. As revealed, the short-range order (SRO) diffuse scattering intensity behaves conditionally as I-SRO(k) alpha k(2) for k -> 0 from all the reciprocal-space directions, which is in contrast to the conventional Huang diffuse scattering intensity conditionally definable as I-Huang(k) proportional to k(-2) for k -> 0. Special attention is paid to the analytic (i.e. azimuthal) and nonanalytic (i.e. first-kind-jump-discontinuous 'radial') behaviours of the Fourier components of interatomic 'mixing' energies or the SRO intensities near and at the Gamma(000)-point.