Magnetic and electrical properties of lanthanum substituted yttrium iron garnets

Polycrystalline yttrium lanthanum iron garnets (Y3LaxFe5-x O12) with varying La substitution (0 ≤ x ≤ 0.5) have been prepared in the pellet form, and studied by X-ray diffraction, magnetization, a.c. susceptibility and electrical resistivity measurements. The lattice constants are determined and the applicability of Vegard’s law has been tested. The saturation magnetization (4 πMS) decreases very slowly almost linearly with increasing x from x = 0.0–0.5 indicating minimal reduction in ferrimagnetism and least magnetic loss. Variation of saturation magnetic moment per formula unit at 300 K with x can be explained satisfactorily assuming the collinear spin-ordering model. The Curie temperature (Tc) reduces very slowly with increasing x, which is consistent with the observed decrease in 4 πMS with x. The activation energy (E) decreases very slowly with increasing x for x > 0.1.