Thermodynamics of a magnetic transition in MnS$_2$ at high pressures

The behavior of the specific heat of MnS$_2$ at high pressures has been studied. A significant increase in the transition temperature $T_{\text{N}}$ to an antiferromagnetic state with the pressure from $48.2$ K at atmospheric pressure to $76$ K at a pressure of $5.3$ GPa has been revealed. The initial pressure derivative is $dT_{\text{N}}/dP=4.83\,$K/GPa. It has been found that the parameter $\alpha = d(\log T_{\text{N}})/d(\log V) = -6.6 \pm 0.1$ is significantly different from the value $\alpha= -10/3\approx -3.3$ (Bloch relation), which is typical of numerous antiferromagnetic insulators–transition-metal oxides and fluorides. The volume jump at the magnetic transition point has been estimated. The necessity of direct dilatometric measurements of the volume has been justified.