Ferromagnetism and structural phase transition in rhombohedral PrIr3

The synthesis, structural, magnetic, thermal, and transport properties are reported for polycrystalline PrIr₃. At room temperature PrIr₃ displays the rhombohedral space group R-3m and a PuNi₃-type structure. At around 70 K a phase transition to a monoclinic $C2/m$ structure is observed and continued cooling reveals temperature independent behavior of the unit cell volume. Further, PrIr₃ undergoes a paramagnetic to ferromagnetic transition with Tc=7.50.16em0exK. The temperature dependent magnetic susceptibility follows the Curie-Weiss law with a positive Curie-Weiss temperature, and an effective moment that is close to the theoretical effective moment for a free Pr⁺³ ion. The structural transition introduces further complexity into the behavior of PuNi₃-type materials and highlights the importance of temperature-dependent structural studies to complement physical property measurements in intermetallic compounds.