Crystal structure, magnetic and magnetocaloric properties of the new orthorhombic Y3Co2-type Gd3Co1+xNi1−x solid solution†

This work reports the existence of the new rare-earth intermetallic compound Gd₃Co_1+xNi_1−x (with x = 0.1, 0.2, 0.3, and 0.4) and the investigation of its crystallographic, magnetic, and magnetocaloric properties. Gd₃Co_1+xNi_1−x is a novel solid solution phase that crystallizes in the orthorhombic Y₃Co₂-type structure [oP20, Pnmm (no. 58)]. It constitutes the first representative of a compound crystallizing in this structural prototype. The research also includes an analysis of the critical behavior associated with the second-order phase transition from a paramagnetic to a ferromagnetic state (PM–FM) detected in the compound. This analysis indicates that short-range order isotropic magnetic interactions are present, consistent with the 3D Heisenberg model. Increasing the Co content leads to a higher Curie temperature (T_C), thus, shifting the peak of the magnetic entropy change, while maintaining the overall physical properties. This demonstrates the potential of tuning the working temperature region by modifying the Co/Ni concentration without negatively affecting the magnetocaloric properties. For μ₀ΔH = 5 T, the magnetic entropy change peaks range between 7.81 and 8.40 J kg⁻¹ K⁻¹, while the refrigerant capacity values are around 600 J kg⁻¹. These results place this family among the top performing ones in their working temperature region. The scaling relations and the universal curve confirm the second-order nature of the phase transition and validate the calculated critical exponents.