Influence of Cr substitution on magnetic and dielectric properties of gadolinium iron garnets

Abstract

Polycrystalline samples of Cr substituted gadolinium iron garnets (GdFe5-xCrxO12; x = 0 to 0.3) were synthesized in single-phase form via solid-state route. The lattice constant, Fe(a)-Fe(d) bond length and Fe(a)-O-Fe(d) bond angle values are found to decrease with increase in Cr concentration. All samples undergo the interesting magnetic compensation behavior close to the room temperature. In addition to that, they also exhibit ferrimagnetic (FIM) transition with decrease in transition temperature (Tc) from 569 K for x = 0 to 518 K for x = 0.3. The observed increase in saturation magnetization at room temperature is explained in terms of preferential occupation of Cr3+ ions at the octahedral site of Fe3+ ions. In addition to magnetic properties, we have also analyzed dielectric and modulus spectra. The room temperature dielectric constant at f = 1 MHz, is found to increase with Cr concentration, i.e. from 15 for x = 0 to 27 for x = 0.3, and it is ascribed to the increase in the charge carriers concentration. Moreover, the modulus data were analyzed using the Bergman function incorporated with the Kohlrausch-Williams-Watts (KWW) function, which suggests that the relaxation dynamics is governed by the short-range movement of charge carriers.