${\mathrm{Cs}}^{133}$ and ${\mathrm{Cl}}^{35}$ NMR in Antiferromagnetic CsNi${\mathrm{Cl}}_3$

The nuclear magnetic resonances of ${\mathrm{Cl}}^{35}$ and ${\mathrm{Cs}}^{133}$ in magnetically ordered CsNi${\mathrm{Cl}}_3$ have been investigated to determine the magnetic structure and magnetic properties of this compound. Both the Cs and Cl resonances have been observed in single crystals over a temperature range 300 to 1.3 °K. These data show that CsNi${\mathrm{Cl}}_3$ undergoes two magnetic transitions, one at (4.84±0.03) °K and the other at (4.40±0.03) °K. The higher-temperature transition corresponds to antiferromagnetic alignment of the Ni spin along the $c$ axis, while the perpendicular part of the moment is probably paramagnetic. At 4.40 °K, the perpendicular component of the moment becomes ordered. The magnetization curves for the perpendicular and parallel components of the Ni moment have been obtained. When normalized to the appropriate Néel temperature, the reduced magnetization curves represented by components of the internal field parallel and perpendicular to the $c$ axis have the same dependence upon temperature, as evidenced by the Cs and Cl resonances. Near the corresponding $T_N$, the critical exponent $\beta$ is 0.32±0.03 for both the parallel and perpendicular components.