Pressure Measurement of SolidHe3through the Magnetic Ordering Temperature

The pressure of solid ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ has been measured as a function of temperature and molar volume down to and through its nuclear ordering temperature. Pressure measurement above the ordering temperature reveals that besides the known $\frac{1}{T}$ term there are a significant negative term in $\frac{1}{T^2}$ and a positive term in $\frac{1}{T^3}$. The observed discontinuous change in pressure through the ordering temperature is discussed in connection with the first-order phase transition.