Abstract
Evidence of elemental copper magnetism in Cu-coated γ-Fe 2 O 3 nanoparticles was revealed by element specific x-ray absorption spectroscopy and magnetic circular dichroism (XMCD). An interfacial layer of magnetic CuO was discovered that interacted with the Fe 3+ surface magnetic moments. This unexpected exchange interaction canted the moments of the CuO, so that a non-zero net magnetic moment was measured. XMCD measurements as a function of field on the copper coated γ-Fe 2 O 3 nanoparticles indicated that the CuO magnetic moment was aligned with the octahedral Fe 3+ and its magnetization was modified by the changing applied field. With increasing copper thickness, a stronger field dependence of the Fe 3+ and Cu 2+ magnetization was observed. © 2012 American Institute of Physics.