Anisotrophic Magnetocaloric Effect in Single Crystalline CoSb$_2$O$_6$

The quasi one-dimensional spin chains of CoSb$_2$O$_6$ are oriented along [110] at $z=0$ and [1$\bar{1}$0] at $z=1/2$. Application of magnetic field $H$ parallel to [110] is therefore parallel to one set of chains and perpendicular to the other. $H>2$ tesla, applied parallel to [110], lowers the N\'eel temperature ($T_N = 13.4$ K) for one set of chains, leaving the other set unaffected. This gives rise to two peaks in the heat capacity $C_P$, which are separated by 3.8 K when $H=8$ tesla. Integrating $C_P(T,H)/T$ with respect to temperature yields a change in entropy $\Delta S_T$, from which the change in \textit{magnetic} entropy $\Delta S_m(\Delta H)=\Delta S_T(H_2)-\Delta S_T(H_1)$, is determined. Near 12 K we find that $\Delta S_m$(8 T) = 2.97 J/kg K for measurements with $H \parallel [110]$ or [$1\bar{1}$0] and $\Delta S_m$(8 T) = 0.44 J/kg K for $H \parallel [001]$. This anisotropy implies that rotation of the sample in \textit{constant} magnetic field could induce a change in sample temperature.