Principal magnetic susceptibilities of MnO and their temperature dependence

Abstract

The temperature dependence of the principal susceptibilities, ${\ensuremath{\chi}}_{\ensuremath{\parallel}}$ and ${\ensuremath{\chi}}_{\ensuremath{\perp}}$, of MnO are reported in the range of 4.2 to 300 K from the studies in a single crystal from which nonstoichiometries have been removed. A procedure combining selective stress applied along [111] during measurements (to remove $T$ domains), field dependence of the magnetization (to remove $S$ domains), and the measurement of the initial $\ensuremath{\chi}$ is used to determine both ${\ensuremath{\chi}}_{\ensuremath{\parallel}}$ and ${\ensuremath{\chi}}_{\ensuremath{\perp}}$ below ${T}_{N}$ (117.9 K). A stress \ensuremath{\le}25 bars is sufficient to remove $T$ domains and a critical field ${H}_{c}\ensuremath{\simeq}2$ kOe is determined from the field dependence of the magnetization for $\stackrel{\ensuremath{\rightarrow}}{\mathrm{H}}\ensuremath{\parallel}(111)$ plane. Comparison of the temperature dependence of ${\ensuremath{\chi}}_{\ensuremath{\perp}}$ in MnO vis-\`a-vis Mn${\mathrm{F}}_{2}$ and RbMn${\mathrm{F}}_{3}$ is made, and it is suggested that the observed differences may at least be partly due to the lattice distortion effects in MnO below ${T}_{N}$. For ${\ensuremath{\chi}}_{\ensuremath{\parallel}}$ in MnO, the data fitted ${T}^{2}$ variation to about $\frac{{T}_{N}}{3}$. Further theoretical work is necessary to explain all the observations in MnO.