Temperature effects in the theory of spin-polarized photoelectron diffraction

Abstract

We outline an extension of the previously-developed zero-temperature spherical-wave single-scattering-cluster theory of spin-polarized photo-electron diffraction (SPPD) to finite temperature. We show explicitly how the spin-spin correlation function ⟨s(r0) · s(r)⟩ enters into the thermal averages over near neighbors, thus allowing SPPD spectra to be computed as a function of temperature if the correlation function is known. The spin-dependent part of the diffraction may be isolated by defining a spin asymmetry for a 3s emission process S3s, which is the ratio of spin-up to spin down intensities as normalized to the high-temperature or paramagnetic limit. A computation of S3s for a standard correlation function derived from a Monte Carlo analysis shows a complex dependence on temperature, but does not exhibit the step-like behavior at temperatures of several times TN where a step has been observed experimentally for KMnF3 and MnO. These results thus confirm that the steps observed in SPPD represent a new effect that goes beyond present theoretical models of the disappearance of shortrange magnetic order.