Enhanced Magnetocaloric Effect from Cr Substitution in Ising Lanthanide Gallium Garnets Ln3CrGa4O12 (Ln = Tb, Dy, Ho)

A detailed study on the crystal structure and bulk magnetic properties of Cr substituted Ising type lanthanide gallium garnets Ln(3)CrGa(4)O(12) (Ln = Tb, Dy, Ho) is carried out using room temperature powder X-ray and neutron diffraction, magnetic susceptibility, isothermal magnetization, and heat capacity measurements. The magnetocaloric effect (MCE) in Ln(3)CrGa(4)O(12) is compared to that of Ln(3)Ga(5)O(12). In lower magnetic fields attainable by a permanent magnet (<= 2 T), Cr substitution greatly enhances the MCE - by 20% for Ln = Dy and 120% for Ln = Ho compared to the unsubstituted Ln(3)Ga(5)O(12). This is likely due to changes in the magnetic ground state as Cr substitution also significantly reduces the frustration in the magnetic lattice for the Ising type Ln(3)Ga(5)O(12).