Jean Pierre Sanchez

Investigation of uranium edges in by x-ray magnetic circular dichroism

We report a high statistic x-ray magnetic circular dichroism study of carried out at the uranium edges. Using the sum rules, the detailed analysis of our data yields orbital and spin moments of the 5f uranium electrons in reasonable agreement with values extracted from a localized moment approach.

Electronic and magnetic properties of the 4f and 5f intermetallics from Mössbauer spectroscopy

Over the years Mossbauer spectroscopy has proved to be an important tool for the study of f-electron systems. Through measurements of the hyperfine interactions, this microscopic technique gives access to the charge state of the resonant atom (isomer shift), to its local symmetry (quadrupole splitting) and to the magnetic moment associated with its open electron shells (magnetic splitting). With the help of a few examples taken from recent work we demonstrate the power of this technique for obtaining information on the electronic and magnetic properties of 4f and 5f intermetallics.

Polarized neutron scattering and x-ray magnetic circular dichroism studies of the heavy-fermion superconductor UNi2Al3

A polarized neutron scattering experiment and an x-ray magnetic circular dichroism (XMCD) study at the M4,5 edges of uranium have been performed on a single crystal of the heavy-fermion superconductor UNi2Al3 in the paramagnetic phase. Projections of the maximum-entropy reconstructions of the magnetization distribution obtained from neutron data evidence a large and almost spherical distribution on the U sites and an induced moment at the Ni sites. Refinements of the magnetic structure factors within the dipolar approximation allow one to quantify the Ni contribution and the orbital and spin uranium moments, and reveal a diffuse contribution parallel to the 5f moment. The XMCD study leads to a value of the 5f orbital contribution in agreement with the neutron one. For both neutron and XMCD experiments, we compare our results with previous measurements performed on the parent compound UPd2Al3.

5f-hybridization in URhAl studied by X-ray magnetic circular dichroism

Abstract We report X-ray magnetic circular dichroism experiments performed at the U–M 4,5 edges of an URhAl single crystal. Thanks to the sum rules, we derive an orbital magnetic moment on the uranium atoms equal to (1.63±0.14) μ B . The comparison of the shape of the M 5 dichroic signal with pure J multiplet calculations shows effects due to 5f-hybridization. However, we found that the contribution of the magnetic dipole term 〈 T Z 〉 to the effective spin moment 〈 S Z eff 〉=〈 S Z 〉+3〈 T Z 〉 is non negligible. These results indicate an higher localization of the 5f-orbitals with respect to other itinerant ferromagnetic actinides compounds such as UFe 2 or UNi 2 .

Orbital and spin moments in uranium compounds from X-ray magnetic circular dichroism

Abstract The knowledge of the orbital ( μ L ) and spin ( μ S ) magnetic moments of a magnetic material is fundamental for the understanding of its basic properties. X-ray Magnetic Circular Dichroism (XMCD) at the uranium M-edges (3.5–3.8 keV) of a ferromagnet is a new tool which provides a direct and independent determination of μ L and μ S using sum rules. Here we report on recent XMCD experiments performed on uranium compounds with different degree of hybridization USb 0.5 Te 0.5 (localized), UFe 2 (strongly hybridized) and US (weakly hybridized). The results are compared to those obtained from the analysis of the magnetic form factor deduced from neutron scattering experiments. The importance of the value assigned to the magnetic spin dipolar operator 〈T z 〉 is emphasized.