Large Magnetocaloric Effect of PrNi Compound at Liquid-Hydrogen Temperatures

In the work, polycrystalline PrNi compound was synthesized by the arc-melting method. The crystal structure is determined as a CrB-type orthorhombic structure (Space group Pnma). The Curie temperature ( $T_{\mathrm {C}}$ ) is determined to be 21.0 K according to the maximum absolute value of the first derivative of magnetization. The slope of the Arrott plots is positive around phase transition temperature, indicating the second-order phase transition (SOPT) characteristic. The magnetic entropy change ( $-\Delta S_{\mathrm {M}}$ ) was calculated from the isothermal magnetization data based on Maxwell's relationship. The maximum value of $-\Delta S_{\mathrm {M}}$ is calculated to be 7.3 and 13.0 J/kg $\cdot \text{K}$ for the magnetic field changes of 0–2 and 0–5 T, respectively. The large magnetocaloric effect (MCE) around 21.0 K with a SOPT feature indicates that PrNi is great potential in the application of magnetic refrigeration for hydrogen liquefaction.