Effect of Particle Size on the Magnetic and Magnetocaloric Properties of Gd_5.09Si_1.88Ge_2.03 Compound

Magnetic refrigeration presents an energy-efficient and environmentally friendly alternative to conventional gas compression refrigeration, mainly driven by the magnetocaloric effect in materials with a first- or second-order phase transition. One of the main obstacles to the development of magnetocaloric refrigerants is the relative difficulty in processing them adequately on a large scale and in suitable geometries. For example, powder metallurgy or a polymer-based composite with magnetocaloric fillers may be a viable alternative to overcome these problems. In this context, this study investigates the influence of particle size on the magnetic and magnetocaloric properties of the Gd5.09Si1.88Ge2.03 compound, with particle sizes of <25 μm, 25–38 μm, and 38–45 μm. For a magnetic field change of 20 kOe, the maximum isothermal entropy change |ΔSTmax| reached 6.3 J kg–1 K–1 for the <25 μm particle size, while the larger sizes (25–38 μm and 38–45 μm) showed |ΔSTmax| values of 7.8 J kg–1 K–1 and 8.1 J kg–1 K–1, respectively. Additionally, the relative cooling power (RCP) reached up to 127 J kg–1 for the particle sizes of 25–38 μm and 38–45 μm, while the particle size of <25 μm resulted in a reduced RCP of 111 J kg–1. A similar trend was observed in the temperature-averaged entropy change (TEC) and maximum refrigerant capacity (RCmax). The results suggest an optimal particle size range >25 μm, beyond which the magnetic and magnetocaloric properties stabilize. These findings are relevant for composite processing techniques, where particle size control is crucial for enhancing the material’s performance.