olivier bengone - Academia.edu (original) (raw)
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Homi Bhabha National Institute (HBNI, BARC, MUMBAI)
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Papers by olivier bengone
The Journal of Physical Chemistry C, 2019
Using first principle calculations, the problem of scaling magnetic properties in nanoparticles i... more Using first principle calculations, the problem of scaling magnetic properties in nanoparticles is addressed. To this aim, the local electronic structure is characterized in cobalt quasi-spherical magnetic nanoparticles, in a large size range, from 0.5 to 2 nm of diameter. First, specific patterns of the magnitude of local spin magnetic moments are evidenced depending on the shape and the size of the nanoparticles. Then, effects of local structural environment (atomic coordination, structural deformations, finite size effects, shape changes) are unravelled. In small icosahedral nanoparticles, the local spin magnetic moment is found to decrease from the surface to the center. General rules driving charge transfers are observed whereby donor atomic sites are exclusively subsurface atoms and more unexpected vertex surface atomic sites. The variation of the magnetic moment is driven by the coupling between cluster microstructure and complex hybridization effects. In larger truncated octahedral clusters, whereas some properties are still found (quasi-zero inter-atomic site charge transfer, the reversal from anti-ferromagnetic to ferromagnetic coupling of electronic sp states with d ones at vertex atomic sites), other vary such as the behavior of the local spin magnetic moment which now presents weak oscillations.
Physical Review B, 2017
We use x-ray magnetic circular dichroism to evidence the effect of correlations on the local impu... more We use x-ray magnetic circular dichroism to evidence the effect of correlations on the local impurity magnetic moment in an archetypal Kondo system, namely, a dilute Cu:Fe alloy. Applying the sum rules on the Fe L 2,3 absorption edges, the evolution of the spin and orbital moments across the Kondo temperature are determined separately. The spin moment presents a crossover from a nearly temperature-independent regime below the Kondo temperature to a paramagneticlike regime above. Conversely, the weak orbital moment shows a temperatureindependent behavior in the whole temperature range, suggesting different Kondo screening temperature scales for the spin and orbital moments.
The Journal of Physical Chemistry C, 2019
Using first principle calculations, the problem of scaling magnetic properties in nanoparticles i... more Using first principle calculations, the problem of scaling magnetic properties in nanoparticles is addressed. To this aim, the local electronic structure is characterized in cobalt quasi-spherical magnetic nanoparticles, in a large size range, from 0.5 to 2 nm of diameter. First, specific patterns of the magnitude of local spin magnetic moments are evidenced depending on the shape and the size of the nanoparticles. Then, effects of local structural environment (atomic coordination, structural deformations, finite size effects, shape changes) are unravelled. In small icosahedral nanoparticles, the local spin magnetic moment is found to decrease from the surface to the center. General rules driving charge transfers are observed whereby donor atomic sites are exclusively subsurface atoms and more unexpected vertex surface atomic sites. The variation of the magnetic moment is driven by the coupling between cluster microstructure and complex hybridization effects. In larger truncated octahedral clusters, whereas some properties are still found (quasi-zero inter-atomic site charge transfer, the reversal from anti-ferromagnetic to ferromagnetic coupling of electronic sp states with d ones at vertex atomic sites), other vary such as the behavior of the local spin magnetic moment which now presents weak oscillations.
Physical Review B, 2017
We use x-ray magnetic circular dichroism to evidence the effect of correlations on the local impu... more We use x-ray magnetic circular dichroism to evidence the effect of correlations on the local impurity magnetic moment in an archetypal Kondo system, namely, a dilute Cu:Fe alloy. Applying the sum rules on the Fe L 2,3 absorption edges, the evolution of the spin and orbital moments across the Kondo temperature are determined separately. The spin moment presents a crossover from a nearly temperature-independent regime below the Kondo temperature to a paramagneticlike regime above. Conversely, the weak orbital moment shows a temperatureindependent behavior in the whole temperature range, suggesting different Kondo screening temperature scales for the spin and orbital moments.