Rare-Earth Doped Gd3−xRExFe5O12 (RE = Y, Nd, Sm, and Dy) Garnet: Structural, Magnetic, Magnetocaloric, and DFT Study

The study reports the influence of rare-earth ion doping on the structural, magnetic, and magnetocaloric properties of ferrimagnetic Gd3−xRExFe5O12 (RE = Y, Nd, Sm, and Dy, x = 0.0, 0.25, 0.50, and 0.75) garnet compound prepared via facile autocombustion method followed by annealing in air. X-Ray diffraction (XRD) data analysis confirmed the presence of a single-phase garnet. The compound’s lattice parameters and cell volume varied according to differences in ionic radii of the doped rare-earth ions. The RE3+ substitution changed the site-to-site bond lengths and bond angles, affecting the magnetic interaction between site ions. Magnetization measurements for all RE3+-doped samples demonstrated paramagnetic behavior at room temperature and soft-ferrimagnetic behavior at 5 K. The isothermal magnetic entropy changes (−ΔSM) were derived from the magnetic isotherm curves, M vs. T, in a field up to 3 T in the Gd3−xRExFe5O12 sample. The maximum magnetic entropy change (−∆SMmax) increased with Dy3+ and Sm3+substitution and decreased for Nd3+ and Y3+ substitution with x content. The Dy3+-doped Gd2.25Dy0.75Fe5O12 sample showed −∆SMmax~2.03 Jkg−1K−1, which is ~7% higher than that of Gd3Fe5O12 (1.91 Jkg−1K−1). A first-principal density function theory (DFT) technique was used to shed light on observed properties. The study shows that the magnetic moments of the doped rare-earths ions play a vital role in tuning the magnetocaloric properties of the garnet compound.