Synthesis and magnetic properties of nano-dimensional Fe 1−x Cu x Al 2 O 4 (0.3 ≤ x ≤ 0.8)

Here we report, the sol–gel synthesized, microstructural analysis, surface and magnetic properties of solid solutions of Fe 1−x Cu x Al 2 O 4 . The singular phase of the samples for x values varied between 0.3 and 0.8 at 700 °C has been obtained. The powder X-ray diffraction, electron diffraction and HRTEM analysis reveal that the particle size systemically increases with the increase in x value. The XPS studies have confirmed the presence of Cu 2+ species with a (Fe + Cu)/Al surface atomic ratio close to the bulk stoichiometric value. Unlike the common magnetic spinels with B-site magnetic cations, Fe 1−x Cu x Al 2 O 4 shows only A-site magnetism in a diamond-type lattice. The samples with smaller particle size, namely the samples for x = 0.3 and 0.4 exhibit small magnetization. The origin of such magnetism is attributed to the inversion in the spinel structure and the defect induced magnetism. Except for the x = 0.7 sample, all other samples show spin glass behavior.