Synthesis of Sm26Co11Ga6-type R26Co5+xIn12-x compounds (RY, Dy–Tm) (x = 0–0.2) and magnetic properties of Tb26Co5In12

Abstract

Ternary rare-earth-based R₂₆Co₅–₆In_12-11 (RY, Tb–Tm) compounds have been prepared by arc melting and subsequent annealing at 870 K. The powder X-ray diffraction analysis reveals that the samples crystallizes in the tetragonal Sm₂₆Co₁₁Ga₆-type structure (space group P4/mbm, N 127, tP86). The lattice parameters follow the lanthanide contraction rule, decreasing from a = 1.19413 nm and c = 1.58441 nm of Tb₂₆Co₅In₁₂ to a = 1.17353 nm and c = 1.56770 nm of Tm₂₆Co_5.2In_11.8. Tb₂₆Co₅In₁₂ is ferromagnetic with the Curie temperature T_C = 72 K, and it shows two mixed ferro-antiferromagnetic ordering at T_m' ∼66 K and T_m = 18 K, respectively. Tb₂₆Co₅In₁₂ displays distinct hard magnet properties, e.g., the coercive field of 18 kOe, the saturation magnetization of 166 μ_B/fu and the theoretical maximum energy product (BH)_max of ∼314 kJ/m³ at 2 K. The magnetocaloric effect of polycrystalline Tb₂₆Co₅In₁₂ has been investigated using magnetic and heat capacity measurements.