Magnetic and electrical properties of lanthanum substituted yttrium iron garnets

Polycrystalline yttrium lanthanum iron garnets (Y₃La_xFe_5-xO₁₂) 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 πM _S) 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 (T _c) reduces very slowly with increasing x, which is consistent with the observed decrease in 4 πM _S with x. The activation energy (E) decreases very slowly with increasing x for x > 0.1.