Principal magnetic susceptibilities of MnO and their temperature dependence

The temperature dependence of the principal susceptibilities, ${\chi }_{\parallel }$ and ${\chi }_{\perp }$, 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 $\chi$ is used to determine both ${\chi }_{\parallel }$ and ${\chi }_{\perp }$ below $T_N$ (117.9 K). A stress ≤25 bars is sufficient to remove $T$ domains and a critical field $H_c\simeq 2$ kOe is determined from the field dependence of the magnetization for $\overrightarrow{\mathrm{H}}\parallel \mathrm{}\left(111\right)\mathrm{}$ plane. Comparison of the temperature dependence of ${\chi }_{\perp }$ in MnO vis-à-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 ${\chi }_{\parallel }$ 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.