Metamagnetic phase transition and corresponding magnetocaloric effect in intermetallic Ho_1-xTb_xCo₂ alloys

A comprehensive investigation was conducted to examine the magnetic properties and magnetocaloric effect (MCE) around the phase transition temperature of the intermetallic Ho_1-xTb_xCo₂ (x=0.05, 0.1, and 0.15) alloys. X-ray diffraction (XRD) investigations reveal that the single-phase alloys crystallize in the cubic phase (space group Fd3̅m) at room temperature and undergo a structural transition to the tetragonal phase (space group I41/amd) below their Curie temperatures. These alloys demonstrated a metamagnetic transition around their respective phase transition temperatures, accompanied by a remarkable MCE and negligible hysteresis loss. The Landau free energy study confirmed the existence of the first-order magnetic transition in the aforementioned samples. The spin reorientation occurring below the transition temperature was observed. The studied alloys displayed significant magnetic entropy change (ΔS_M) values of 15.6 JKg⁻¹K⁻¹, 15.2 JKg⁻¹K⁻¹, and 13.06 JKg⁻¹K⁻¹ in a wide temperature span over 20 K under a magnetic field change (ΔH) of 5 T for x=0.05, 0.1, and 0.15, respectively. Furthermore, large refrigerant capacities (RC) of 323.6 Jkg⁻¹, 311.28 Jkg⁻¹, and 323.46 Jkg⁻¹ were achieved under ΔH=5 T for these alloys. An unexpected asymmetric broadening of the ΔS_M peak was observed as the magnetic field increased. A significant change in the adiabatic temperature (ΔT_ad) of 5.3–6 K was achieved under ΔH=5 T. The outstanding magnetocaloric performance of studied materials may make them promising for magnetic refrigeration applications within the 87–105 K temperature range.