Magnetic structure of Fe-doped CoFe2O4 probed by x-ray magnetic spectroscopies

The magnetic properties of iron-doped cobalt ferrite (Co 1-xFe2+xO4) (001) thin films grown epitaxially on MgO (001) substrates are investigated by superconducting quantum interference device magnetometry and soft x-ray magnetic linear and circular dichroisms. All Co1-xFe2+xO4 (0.01 ≤ x ≤ 0.63) samples have out-of-plane magnetic easy axes and large coercive fields, unlike Fe 3O4, due to a large Co2⁺ orbital moment. The magnetic moments for those samples are significantly reduced from their bulk values; however, as x increases, the magnetic moments tend nearer to their bulk values and increase more rapidly as x approaches 1. This reduction in magnetic moment is attributed to spin canting among the Co2⁺ cations, owing to a small in-plane tensile strain in the film and to an increased antiferromagnetic alignment among all the cations caused by a partially inverse spinel cubic structure and the likely presence of antiphase boundaries. Our results show that small changes in stoichiometry can lead to significant changes in the magnetic moment of Co1-xFe2+xO4, especially at large values of x. © 2011 American Physical Society.

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Author Divine P Kumah Physics