Investigation of negative magnetization and impedance spectroscopy of Sm-substituted gadolinium iron garnets

Samarium substituted gadolinium iron garnet $(G{d}_{3-x}S{m}_{x}F{e}_{5}O{}_{12};x=0-0.3)$ samples were synthesized in pure-phase form by solid-state chemical reaction method. The lattice constant increases (12.4624 Å to 12.5211 Å) with Sm-concentration. Magnetization measurements show an increase in ferrimagnetic (FIM) transition temperature (T _C = 567 K to 575 K) and a decrease in magnetic compensation temperature (T _comp = 286 K to 70 K) upon Sm-substitution. In addition to magnetic compensation, an interesting negative magnetization under field-cooled condition is achieved for a sample with x = 2.0, and it has been explained in terms of enhanced magnetic anisotropy due to Sm-substitution. A significant increase in saturation magnetization is attained at room temperature by Sm-substitution. Frequency dependence of complex impedance shows relaxation behavior and the relaxation frequency follows the Arrhenius power-law, along with an anomaly around FIM T _C. Such anomaly is ascribed to magneto-electric coupling. (paper)