X-Ray Magnetic Circular Dichroism Studies of FeRh Nanoparticles

Fe_xRh_100-x (x = 50, 80) nanoparticles (NPs) with an average diameter of ~2 nm were prepared by simultaneous decomposition of stoichiometric quantities of Fe[N(Si(CH₃)₃)₂]₂ and Rh(C₃H₅)₃ using two different routes: 1) a standard hydrogenation procedure and 2) a new one based on use of amino-borane as a reducing agent. All samples were found to be superparamagnetic with a blocking temperature below 10 K. Results of X-ray magnetic circular dichroism (XMCD) experiments at the Fe K-edge and the Rh L_2,3 edges have shown that not only iron but also rhodium atoms are magnetic as a result of hybridization of Fe 3d states with 4d states of Rh. The total induced magnetic moment of Rh atoms as well as its spin and orbital contributions are shown to depend on chemical composition of NP_S and the preparation method.