Magnetic and electrical properties of aluminium and chromium co-substituted yttrium iron garnets

Abstract

Polycrystalline yttrium aluminium-chromium iron garnets (Y 3 Al x Cr x Fe 5 − 2 x O 12 ) with varying Al-Cr substitution (0 ≤ x ≤ 1.0) 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 (4π M s ) decreases linearly with increasing x from x = 0.1 to 1.0 indicating reduction in ferrimagnetic behaviour. 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 ) decreases with increasing x which is consistent with the observed decrease in 4π M s with x . The activation energy ( E ) initially increases up to x = 0.6 and thereafter it levels off for further increase in x > 0.6.