Giant Magnetocaloric Effect in Cr- and Fe-Substituted Frustrated Magnet Gadolinium Gallium Garnets, Gd3Ga5O12, for Magnetic Cooling at Cryogenic Temperatures

Abstract

The beneficial effects of Cr and Fe substitutions in enhancing the magnetocaloric properties of the frustrated magnetic system gadolinium gallium garnets Gd3Ga5O12, i.e., Gd3CrGa4O12 and Gd3FeGa4O12, are discussed for their potential use as magnetic refrigerant materials. Evaluations of their structural, electronic, magnetic, and thermal properties were carried out to investigate the effect of magnetic ion substitution in the frustrated magnetic lattice and its magnetocaloric properties. For both Cr and Fe substitutions, the cubic Ia3d structure remains preserved, and antiferromagnetic correlations are observed with very negligible magnetic hysteresis at low temperatures. A maximum isothermal magnetic entropy change, - Delta S m max similar to 49.60 J / kg K , adiabatic temperature change, Delta T ad max similar to 14.1 K , and relative cooling power, RCPmax similar to 645.53 J/kg for Gd3CrGa4O12 and - Delta S m max similar to 35.3 J / kg K , Delta T ad max similar to 12.1 K , and RCPmax similar to 549.72 J/kg for Gd3CrGa4O12 systems are observed, respectively, under a magnetic field change of 9 T. This significant enhancement in the magnetic entropy of the Cr substituted system could be attributed to the changing nature of the magnetic ground state and the considerable change in magnetic frustration that enhances the Gd spin loop. The presence of giant magnetocaloric parameters makes both systems promising competitors in the field of magnetic refrigeration technology for cooling applications at cryogenic temperatures.