Physical properties of RIr₃ (R = Gd, Tb, Ho) compounds with coexisting polymorphic phases

The binary compounds GdIr₃, TbIr₃ and HoIr₃ are synthesized successfully and found to form with macroscopic co-existence of two polymorphic phases: AuBe₅ (C15b) and AuCu₃-type. The dc magnetization and heat capacity studies confirm that the C15b phase orders ferromagnetically, whereas the AuCu₃ phase remains paramagnetic down to 2 K. The frequency dependent ac-susceptibility data, time dependent magnetic relaxation behavior and magnetic memory effect studies suggest that TbIr₃ and HoIr₃ are cannonical spin-glass systems, but no glassy feature could be found in GdIr₃. The critical behavior of all three compounds has been investigated using the magnetization and heat capacity measurements around the transition temperature (T_C). The critical exponents α, β, γ and δ have been estimated using different techniques such as the Arrott-Noakes plot, Kouvel-Fisher plot and critical isotherm as well as analysis of specific heat data and study of magnetocaloric effect. The critical analysis study identifies the type of universal magnetic class in which the three compounds belong.