Enhanced magnetocaloric effect in aluminum doped Gd3Fe5-xAlxO12 garnet: Structural, magnetic, and Mossbauer study

We report a detailed structural, magnetic, and magnetocaloric study on the Aluminum substituted Gadolinium iron garnet. Gd3Fe5-xAlxO12 nanocrystalline powders prepared by auto combustion method followed by sintering at 1100 degrees C were all single-phase with cubic Ia (3) over bard symmetry. The lattice parameter and cell volume decreased upon Al3+ substitution. The X-ray diffraction, temperature, and field-dependent magnetization data, Mossbauer spectroscopy complemented with first-principles density functional calculation (DFT) provided evidence of Al3+ substitution at the tetrahedral site for x <= 0.5 and partial substitution at both tetrahedral and octahedral sites for x = 1 sample. With the substitution of Al3+ at the spin-down tetrahedral Fe3+ site, the saturation magnetization increased. The Gd3Fe5-xAlxO12 samples presented ferrimagnetic ordering at low temperatures. The maximum magnetic entropy change, derived from magnetic isotherms in field up to 3T, in Gd3Fe5-xAlxO12, was observed to vary from similar to 1.94 to , similar to 3.07 J kg(-1) K-1 for x = 0.0 and x = 1.0, respectively. While the maximum relative cooling power value of 226 J kg(-1) was measured for x = 0.25 sample. The magnetocaloric peak's genesis is linked to the Gd sublattice's enhanced magnetism and ferromagnetic ordering at low temperatures.

Automated summary

In this study, a detailed investigation on the structural, magnetic, and magnetocaloric properties of Aluminum substituted Gadolinium iron garnet was conducted. The results showed that Aluminum substitution affected the lattice parameters and saturation magnetization. The substituted samples exhibited ferrimagnetic ordering at low temperatures and demonstrated significant magnetocaloric effects.