Unveiling the Structural, Electronic and Magnetic Properties of Gd4.5A0.5Si3O13 (A = K, Na, and Li) Oxides With Promising Potential for Low‐Temperature Magnetic Cooling

Abstract 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 Gd 4.5 A 0.5 Si 3 O 13 ( 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 P 6 3 / m ), exhibiting an antiferromagnetic semiconductor ground state with magnetic ordering temperatures below 1.8 K (typically ≈0.7 K for Gd 4.5 K 0.5 Si 3 O 13 ). Furthermore, their remarkable maximum magnetic entropy change (−Δ S M max ) values of 31.85 and 58.22 J kgK −1 for Gd 4.5 K 0.5 Si 3 O 13 ; 25.31 and 55.01 J kgK −1 for Gd 4.5 Na 0.5 Si 3 O 13 ; and 25.15 and 55.77 J kgK −1 for Gd 4.5 Li 0.5 Si 3 O 13 , under the magnetic field changes of 0‐2 and 0‐5 T, respectively, surpass those of prominent low‐temperature MCMs, including the commercialized Gd 3 Ga 5 O 12 (≈14.6 and 32.8 J kgK −1 ) paramagnetic salt. These findings in addition to their high environmental stability position these Gd 4.5 A 0.5 Si 3 O 13 oxides as exceptionally promising for practical magnetic cooling applications.