A5045311408- Advanced Condensed Matter Physics
- Multiferroics and related materials
- Physics of Superconductivity and Magnetism
- Magnetic and transport properties of perovskites and related materials
- Thermal Expansion and Ionic Conductivity
- Nuclear materials and radiation effects
- Copper-based nanomaterials and applications
- Theoretical and Computational Physics
- Magnetic properties of thin films
- Iron oxide chemistry and applications
- Catalysis and Oxidation Reactions
- Transition Metal Oxide Nanomaterials
- Inorganic Fluorides and Related Compounds
- Rare-earth and actinide compounds
- Advanced Thermoelectric Materials and Devices
- Mineralogy and Gemology Studies
- Organic and Molecular Conductors Research
- Microwave Dielectric Ceramics Synthesis
- ZnO doping and properties
- Perovskite Materials and Applications
- Magnetic Properties and Synthesis of Ferrites
- Ga2O3 and related materials
- Electronic and Structural Properties of Oxides
- Geomagnetism and Paleomagnetism Studies
- High-pressure geophysics and materials
Centre National de la Recherche Scientifique
2009-2024
Université Grenoble Alpes
2020-2024
Institut Néel
2009-2024
University of Edinburgh
2016-2021
École Nationale Supérieure d'Ingénieurs de Caen
2009-2016
University of Houston
2013-2014
Laboratoire de Cristallographie et Sciences des Matériaux
2009-2011
Université Joseph Fourier
2009
Co$^{2+}$ ions in an octahedral crystal field, stabilise a j$_{eff}$ = 1/2 ground state with orbital degree of freedom and have been recently put forward for realising Kitaev interactions, prediction we tested by investigating spin dynamics two cobalt honeycomb lattice compounds, Na$_2$Co$_2$TeO$_6$ Na$_3$Co$_2$SbO$_6$, using inelastic neutron scattering. We used linear wave theory to show that the magnetic spectra can be reproduced Hamiltonian including dominant nearest-neighbour...
The semivalent oxyphosphate V2OPO4 is found to have long-range V2+/V3+ charge ordering up 605 K where a monoclinic tetragonal structural transition and switch from positive negative thermal expansion are observed. V-V bonding within orbital polymer chains proposed as the key factor in novel of behavior, loss enables transverse oxygen motions dominate at high temperatures. Ferrimagnetic order V2+ spin V3+ down states observed below magnetic 164 K, susceptibility measurements evidence local...
Abstract The nature of the Verwey transition occurring at T V ≈ 125 K in magnetite (Fe 3 O 4 ) has been an outstanding problem over many decades. A complex low temperature electronic order was recently discovered and associated structural fluctuations persisting above are widely reported, but origin underlying correlations hence remains unclear. Here we show that local emerge below Curie C 850 K, through X-ray pair distribution function analysis. Around 80% proportion to magnetization . This...
CoO has an odd number of electrons in its unit cell, and therefore is expected to be metallic. Yet, strongly insulating owing significant electronic correlations, thus classifying it as a Mott insulator. We investigate the magnetic fluctuations using neutron spectroscopy. The strong spatially far-reaching exchange constants reported [Sarte et al. Phys. Rev. B 98 024415 (2018)], combined with single-ion spin-orbit coupling similar magnitude [Cowley 88, 205117 (2013)] results mixing between...
Complex charge and orbital molecule order observed in natural magnetite comparable to meteoritic samples is the most complex electronic known occur naturally.
Neutron spectroscopy was applied to study the magnetic interactions of orbitally degenerate ${\mathrm{Co}}^{2+}$ on a host MgO rocksalt lattice where no long-range spin or orbital order exists. The paramagnetic nature substituted monoxide ${\mathrm{Co}}_{0.03}{\mathrm{Mg}}_{0.97}\mathrm{O}$ allows for disentanglement exchange and spin-orbit interactions. By considering prevalent excitations from pairs, we extract seven constants out fourth coordination shell. An antiferromagnetic...
The antiferromagnetic mixed valence ternary oxide $\alpha$-CoV$_{3}$O$_{8}$ displays disorder on the Co$^{2+}$ site that is inherent to $Ibam$ space group. zero field structural and dynamic properties of $\alpha$-CoV$_{3}$O$_{8}$~have been investigated using a combination neutron x-ray diffraction, DC susceptibility, spectroscopy. low temperature magnetic are consistent with random macroscopic distribution over 16$k$ metal sites. However, by applying sum rules scattering we observe...
${\mathrm{VI}}_{3}$ is a ferromagnet with planar honeycomb sheets of bonded ${\mathrm{V}}^{3+}$ ions held together by van der Waals forces. We apply neutron spectroscopy to measure the two-dimensional ($J/{J}_{c}\ensuremath{\approx}17$) magnetic excitations in ferromagnetic phase, finding two energetically gapped ($\mathrm{\ensuremath{\Delta}}\ensuremath{\approx}{k}_{B}{T}_{c}\ensuremath{\approx}55\phantom{\rule{0.28em}{0ex}}\mathrm{K}$) and dispersive excitations. multilevel spin-wave...
Single crystals of polar LiCrP2O7 were grown by using a top-seeded solution growth method. In addition to the crystal structure, detailed magnetic measurements reveal anisotropic behavior with spin-flop transition. Piezoelectric, polarization, and heat capacity also taken on single crystals. Powder second-harmonic generating measurements, 1064 nm radiation, revealed type 1 phase-matching an efficiency approximately 30 × α-SiO2.
Magnetic quantum oscillations (MQO) provide a common tool to probe the electronic structure of various conductors. The Fermi surface most metals is now known due MQO. This more precise than its alternatives, but requires low temperatures, clean samples and rather strong magnetic fields. In this paper MQO Hall coefficient are measured in rare-earth tritelluride ${\mathrm{TmTe}}_{3}$ shown be much stronger persist higher temperature Shubnikov-de Haas oscillations. amplitude enhancement...
The ferroelectric and spin glass properties of CuFe0.5V0.5O2 have been studied. Magnetization, ac magnetic susceptibility specific heat measurements reveal a behavior (Tf = 20.5 K) for this delafossite. In CuFeO2, substitution trivalent diamagnetic cations Fe3 + is known to change the antiferromagnetic state induce ferroelectricity. But partial occupation site by V3 responsible disordered magnetism in CuFe0.5V0.5O2. dielectric permittivity shows frequency dependence reminiscent relaxor...
Abstract Charge ordering creates a spontaneous array of differently charged ions and is associated with electronic phenomena such as superconductivity, colossal magnetoresistances (CMR), multiferroicity. orders are usually suppressed by chemical doping site selective charge ordered has not previously been demonstrated. Here we show that oxidation one out eight distinct Fe 2+ sites occurs within the complex /Fe 3+ structure 2%-doped magnetite (Fe 3 O 4 ), while rest orbitally network remains...
In order to get the bottom of substitution effects reported in CuCrO${}_{2}$ delafossite, structural, magnetic, and electric properties several CuCr${}_{1\ensuremath{-}x}$M${}_{x}$O${}_{2}$ series, where M${}^{3+}$ is a $S$ $=$ 0 cation (M${}^{3+}$ Al${}^{3+}$, Ga${}^{3+}$, Sc${}^{3+}$, Rh${}^{3+}$), have been investigated. It shown that homogeneity element dependent particularly difficult achieve for smallest Al${}^{3+}$ cation. Ferroelectricity dielectric are found depend on $x$ value, but...
V $3d$ charge and orbital states in ${\mathrm{V}}_{2}{\mathrm{OPO}}_{4}$ have been investigated by means of x-ray absorption spectroscopy (XAS). The electronic structure is very unique that the transfer between ${\mathrm{V}}^{2+}$ ${\mathrm{V}}^{3+}$ face-sharing ${\mathrm{VO}}_{6}$ chains provides negative thermal expansion as reported E. Pachoud et al. [J. Am. Chem. Soc. 140, 636 (2018)]. near-edge region O $1s$ XAS exhibits three features which can be assigned to transitions $2p$ mixed...
Geometrical frustration, as in pyrochlore lattices made of corner-sharing tetrahedra, precludes the onset conventional magnetic ordering, enabling stabilization fluctuating spin states at low temperature. Disorder is a subtle ingredient that can modify nature these exotic nonordered phases. Here, we study interplay between disorder and frustration new ${\mathrm{Tb}}_{2}{\mathrm{ScNbO}}_{7}$ where nonmagnetic site presents charge ${\mathrm{Nb}}^{5+}/{\mathrm{Sc}}^{3+}$. Its quantification...
Negative volume expansion between 620 and 800 K in V2OPO4 is discovered to be of electronic origin due the charge ordering transition at 605 K. Domain reorientation coexistence low high temperature phases close are observed X-ray diffraction data from single crystals grown by chemical vapour transport.
$\alpha$-CoV$_{2}$O$_{6}$ consists of $j_{\mathrm{eff}}={1 \over 2}$ Ising spins located on an anisotropic triangular motif with magnetization plateaus in applied field. We combine neutron diffraction low temperature to investigate the magnetic periodicity vicinity these plateaus. find steps be characterized by metastable and spatially short-range ($\xi\sim$ 10 $\r{A}$) correlations antiphase boundaries defining a local $\langle \hat{T}^{2} \rangle =\ \uparrow \downarrow$ \hat{T}^{3}...
The effect of the rhodium for chromium substitution in AgCr1–xRhxS2 on magnetic and dielectric properties has been studied 0.0 ≤ x 0.5 range. It is found that antiferromagnetic transition temperature TN decreases as increases by about −0.9 K per %Rh up to = 0.30. Consequently, peak real part permittivity, associated with TN, observed decrease same amount. Moreover, electrical polarization magnitude induced below this pyroelectric sulfide tends increasing. This consistent structural study...
Magnetic quantum oscillations (MQO) of Hall coefficient are measured in rare-earth tritelluride TmTe$_{3}$ and shown to be much stronger persist higher temperature than the Shubnikov oscillations. It is general for MQO strongly anisotropic metals, combined measurements diagonal magnetoresistance provide useful informations about electronic structure. The ratio their amplitudes depends linearly on magnetic field, its slope gives a simple accurate measurement tool electron mean free time dependence.