Unveiling the structural phase transition and magnetic structure of ternary boride PrIr₃B₂

We present a comprehensive study of PrIr₃B₂, which includes a detailed investigation of its crystal and magnetic structure using neutron diffraction. AC and DC magnetization and heat capacity data reveal antiferromagnetic ordering at T _N = 10 K. The heat capacity measurements further exhibit a broad peak near 270 K which is related to a structural transition from P6/mmm to C2/m seen in low temperature x-ray diffraction and neutron diffraction. High intensity neutron diffraction data confirm the long-range ordering of Pr³⁺ spins, with no apparent magnetic moment on either of the Iridium sites. Two possible magnetic structures with either k ₁ = [1,0,0] or k ₂ = [½,½,0] fit nearly equally well the neutron diffraction data. However, based on previous magnetization studies on a single crystalline sample it is argued that the second solution with k ₂ corresponds to the appropriate magnetic structure of PrIr₃B₂ below 10 K. In this magnetic structure, the Pr³⁺ moments are oriented at ∼45° to both the a and b axes, with the c-axis being the hard axis of magnetization.