Enhanced Orbital Magnetism inFe50Pt50Nanoparticles

Abstract

X-ray absorption and magnetic circular dichroism spectra at both the Fe and Pt $L_{3,2}$ edges were measured on wet-chemically synthesized monodisperse ${\mathrm{Fe}}_{50}{\mathrm{Pt}}_{50}$ particles with a mean diameter of 6.3 nm before and after complete removal of the organic ligands and the oxide shell covering the particles by soft hydrogen plasma resulting in a pure metallic state. After thermal treatment of the metallic particles, the coercive field increased by a factor of 6, the orbital magnetic moment at the Fe site increased by 330% and is reduced at the Pt site by 30%, while the effective spin moments did not change. A decrease of the frequency of oscillations in the extended x-ray absorption fine structure at the Pt $L_{3,2}$ edges provides evidence for crystallographic changes towards the $L{1}_0$ phase.