Magnetic susceptibility of ${\mathrm{Cs}}_2$Cr${\mathrm{Cl}}_5$.4${\mathrm{H}}_2$O: Interplay of exchange and crystal-field effects

The single-crystal susceptibilities of ${\mathrm{Cs}}_2$Cr${\mathrm{Cl}}_5$.4${\mathrm{H}}_2$O are reported over the temperature interval 40 mK—4.2 K. Long-range magnetic ordering is found to occur at 0.185±0.005 K. Successful data analysis has been carried out in terms of a spin $S=\frac{3}{2}$ Heisenberg linear-chain antiferromagnet with crystal-field and exchange energies of comparable magnitude; the resulting parameters are $g_z=1.98\mathrm{}$, $g_{\perp }=1.95\mathrm{}$, $\frac{D}{k_B}=-0.16\mathrm{}$ K, $\frac{E}{k_B}=-0.05\mathrm{}$ K, and $\frac{J}{k_B}=-0.045\mathrm{}$ K.