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 Gd3Co1+xNi1−x (with x = 0.1, 0.2, 0.3, and 0.4) and the investigation of its crystallographic, magnetic, and magnetocaloric properties. Gd3Co1+xNi1−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 (TC), 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.