Local Antiferromagnetic Order in Single-Crystal MnO above the Néel Temperature

Abstract

This investigation of the spin arrangement in a single crystal of MnO above the N\'eel temperature (${T}_{N}\ensuremath{\simeq}122$\ifmmode^\circ\else\textdegree\fi{}K) has shown that the magnetic neutron scattering in the vicinity of the (111) magnetic peak position consists of diffuse but distinct satellites. The presence of these satellites, which are lined up approximately along a 111g axis of the single crystal, indicates that small regions containing antiphase boundaries and strong antiferromagnetic order exist well above ${T}_{N}$. Applying a model developed for domains in ordered alloys, the average domain size was estimated to be 46 \ifmmode\pm\else\textpm\fi{}5 \AA{} at 133\ifmmode^\circ\else\textdegree\fi{}K. The general features of the scattering indicate that the number of coherent domains in a given region is small, and lead to the preliminary conclusion that the local order in MnO above ${T}_{N}$ is inhomogeneous.