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CoRh alloy nanoparticles (NPs) show nontrivial correlations between chemical and magnetic order that lead to a remarkable nonmonotonous dependence of the magnetic anisotropy energy as a function of composition. Combining experiment and theory we demonstrate how the induced 4d moments and the 3d-4d interfaces control the magnetoanisotropic behavior. New possibilities of tailoring the magnetic characteristics of NPs are thus opened. [ABSTRACT FROM AUTHOR]

Abstract: Oxide free core–shell nanoparticles with an average diameter of about 2nm were wet-chemically synthesised with two different morphologies: either with Rh-rich or an Fe-rich core. The magnetic properties of these nanoparticles were investigated between 5 and 290K by ferromagnetic resonance and superconducting quantum interference device magnetometry. The magnetic anisotropy field varied by a factor of 2 in this temperature range. The nanoparticles with Rh-rich core were found to have a higher anisotropy field of at 5K as compared to the nanoparticles with Fe-rich core (). Multifrequency ferromagnetic resonance (4–24GHz) was used to determine the g-factor. It was determined that the g-factor of nanoparticles with Fe-rich core is higher () compared to nanoparticles with Rh-rich core , being close to the value for iron bulk. [Copyright &y& Elsevier]

The magnetism of bimetallic CoxM1-x (M: Ru and Rh) clusters has been investigated on systems of nanoparticles with diameters smaller than 2 nm embedded in a polymer obtained by means of organometallic synthesis. Whatever the composition (up to x=0.75), the investigation of magnetism evidence a ferromagnetic behavior. As a consequence of size reduction, both CoRh and CoRu systems display enhanced magnetic moments and anisotropy compared to bulk values. [Copyright &y& Elsevier]