Disorder-tuned magnetism and magnetocaloric response in a layered SrGd2Al2O7 single crystal

We report the magnetic and magnetocaloric responses of SrGd 2 Al 2 O 7 single crystals, a Ruddlesden-Popper oxide that exhibits intrinsic A-site cation disorder. Structural analysis reveals significant Sr-Gd intermixing, which suppresses long-range magnetic order down to at least 2 K and preserves the full magnetic entropy reservoir of Gd 3+ . To describe the magnetization behavior, we implement a Gaussian-averaged Brillouin (GAB) framework that accounts for the magnetic bond probability and exchange-strength variance arising from the crystallographic disorder. SrGd 2 Al 2 O 7 exhibits large magnetocaloric responses, achieving a maximum isothermal magnetic entropy change ΔS mag = 42.6 J kg −1 K −1 and adiabatic temperature change T ad = 22.0 K at 7 T, surpassing the benchmark coolant Gd 3 Ga 5 O 12 under comparable conditions. The lattice entropy contribution is exceptionally low below 20 K, further establishing SrGd 2 Al 2 O 7 as a highly competitive cryogenic refrigerant and highlighting controlled structural disorder as a potent design strategy for high-performance magnetocaloric materials.