Assessment of the U and Co magnetic moments in UCoGe by X-ray magnetic circular dichroism

Abstract

The ferromagnetic superconductor UCoGe has been investigated by high field X-ray magnetic circular dichroism (XMCD) at the U-M${}_{4,5}$ and Co/Ge-K edges. The analysis of the branching ratio and XMCD at the U-M${}_{4,5}$ edges reveals that the U-5$f$ electrons count is close to 3. The orbital ($\sim 0.70{\mu }_B$) and spin ($\sim -0.30{\mu }_B$) moments of U at 2.1K and 17T (H//c) have been determined. Their ratio ($\sim -2.3$) suggests a significant delocalization of the 5$f$ electron states. The similar field dependences of the local U/Co and the macroscopic magnetization indicate that the Co moment is induced by the U moment. The XMCD at the Co/Ge-K edges reveal the presence of small Co-4$p$ and Ge-4$p$ orbital moments parallel to the macroscopic magnetization. In addition, the Co-3$d$ moment is estimated to be at most of the order of 0.1${\mu }_B$ at 17T. Our results rule out the possibility of an unusual polarisability of the U and Co moments as well as their antiparallel coupling. We conclude that the magnetism which mediates the superconductivity in UCoGe is driven by U.

arXiv comment4 figures + supplementary material

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Cited by in corpus (11)

• Superconductivity in Uranium Ferromagnets
• Synchrotron Radiation Techniques and their Application to Actinide Materials
• Determination of spin and orbital magnetization in the ferromagnetic superconductor UCoGe
• Switching of magnetic ground states across the UIr1-xRhxGe alloy system
• Effect of Pressure on Magnetism of UIrGe
• Pairing interaction in superconducting UCoGe tunable by magnetic field
• Metamagnetic phase transition in ferromagnetic superconductor URhGe
• Single ferromagnetic fluctuations in UCoGe revealed by 73Ge- and 59Co-NMR studies
• Effect of lattice distortion on U magnetic moments in ${\mathrm{U}}_4\mathrm{R}{\mathrm{u}}_7\mathrm{G}{\mathrm{e}}_6$ studied by polarized neutron diffraction
• Nuclear spin-lattice relaxation time in UCoGe
• Gradual localization of 5f states in orthorhombic UTX ferromagnets - polarized neutron diffraction study of Ru substituted UCoGe