Characterization of the magnetic entropy of double perovskite (Sr1.55Gd0.15Ba0.3)FeMoO6

Double perovskite compounds Sr2FeMoO6 (SFMO) and (Sr1.55Gd0.15Ba0.3)FeMoO6 (SGBFMO) are prepared by standard solid-state reaction. X-ray powder diffraction patterns show that both samples crystallize in the single phase, and they belong to the I4/m space group. The Fe/Mo orders η are 91.7 (3)% for SFMO and 86.2 (3)% for SGBFMO. The Curie temperatures (TC) are 394 K for SFMO and 382 K for SGBFMO. The maximum entropy changes are |SMmax| = 2.13 J K−1 kg−1 for SFMO at 394 K and |SMmax| = 1.98 J K−1 kg−1 for SGBFMO at 382 K |SMmax| decreases, but the curve of magnetic entropy change (MEC) becomes broader for SGBFMO. The proportions of Fe3+/Fe2+ and Mo5+/Mo6+ in SFMO are 2.190121 and 2.022055, respectively, whereas those in SGBFMO are 1.130396 and 3.295191, respectively. Sufficiently large spontaneous magnetization and abrupt drop in magnetization at TC are the two necessary prerequisites for large MEC.