Ground-state wave function of plutonium in PuSb as determined via x-ray magnetic circular dichroism

Abstract

Measurements of x-ray magnetic circular dichroism (XMCD) and x-ray absorption near-edge structure (XANES) spectroscopy at the Pu ${M}_{4,5}$ edges of the ferromagnet PuSb are reported. Using bulk magnetization measurements and a sum rule analysis of the XMCD spectra, we determine the individual orbital [${\ensuremath{\mu}}_{\mathrm{L}}=2.8(1){\ensuremath{\mu}}_{\mathrm{B}}/\mathrm{Pu}$] and spin moments [${\ensuremath{\mu}}_{\mathrm{S}}=\ensuremath{-}2.0(1){\ensuremath{\mu}}_{\mathrm{B}}/\mathrm{Pu}$] of the Pu $5f$ electrons. Atomic multiplet calculations of the XMCD and XANES spectra reproduce well the experimental data and are consistent with the experimental value of the spin moment. These measurements of $\ensuremath{\langle}{L}_{z}\ensuremath{\rangle}$ and $\ensuremath{\langle}{S}_{z}\ensuremath{\rangle}$ are in excellent agreement with the values that have been extracted from neutron magnetic form factor measurements, and confirm the local character of the $5f$ electrons in PuSb. Finally, we demonstrate that a split ${M}_{5}$ as well as a narrow ${M}_{4}$ XMCD signal may serve as a signature of $5f$ electron localization in actinide compounds.