The growing demand for solid-state magnetic cooling, leveraging the magnetocaloric effect requires the discovery of high-performing magnetocaloric materials (MCMs). Herein, a family of Gd-containing MCMs is provided, specifically the Gd4.5A0.5Si3O13 (A = K, Na, and Li) oxides, which demonstratse exceptional low-temperature magnetocaloric performance. Through comprehensive experimental investigations and theoretical calculations on their structural, electronic, and magnetic properties, it is unequivocally confirmed that all of them crystallize in a hexagonal apatite-type structure (space group P63/m), exhibiting an antiferromagnetic semiconductor ground state with magnetic ordering temperatures below 1.8 K (typically ≈0.7 K for Gd4.5K0.5Si3O13). Furthermore, their remarkable maximum magnetic entropy change (-ΔSM max) values of 31.85 and 58.22 JkgK-1 for Gd4.5K0.5Si3O13; 25.31 and 55.01 JkgK-1 for Gd4.5Na0.5Si3O13; and 25.15 and 55.77 JkgK-1 for Gd4.5Li0.5Si3O13, under the magnetic field changes of 0-2 and 0-5 T, respectively, surpass those of prominent low-temperature MCMs, including the commercialized Gd3Ga5O12 (≈14.6 and 32.8 JkgK-1) paramagnetic salt. These findings in addition to their high environmental stability position these Gd4.5A0.5Si3O13 oxides as exceptionally promising for practical magnetic cooling applications.
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