Spin correlations in MnO

Abstract

Spin correlations have been investigated in powder samples of $\mathrm{MnO}$ above and below the Néel temperature by means of diffuse neutron scattering measurements. There is a significant local order above ${\mathrm{T}}_{\mathrm{N}}$, with the spins coupled in an antiferromagnetic fashion and tending to lie parallel to $\left\{111\right\}$ planes. This layer structure suggests a second neighbor interaction energy, with ${\mathrm{V}}_2=4.9\times {10}^{-3}\mathrm{eV}$ and with the exchange interaction ${\mathrm{J}}_2=-4.6°$. There was no evidence for an extra total scattering in the vicinity of the critical temperature.