A5003240310- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Iron-based superconductors research
- Rare-earth and actinide compounds
- Magnetic and transport properties of perovskites and related materials
- Magnetism in coordination complexes
- Magnetic properties of thin films
- High-pressure geophysics and materials
- Organic and Molecular Conductors Research
- Superconducting Materials and Applications
- Inorganic Fluorides and Related Compounds
- Intellectual Capital and Performance Analysis
- Advanced NMR Techniques and Applications
- Lanthanide and Transition Metal Complexes
- Superconductivity in MgB2 and Alloys
- Advanced Thermoelectric Materials and Devices
- Theoretical and Computational Physics
- Atomic and Subatomic Physics Research
- Inorganic Chemistry and Materials
- Thermal Expansion and Ionic Conductivity
- Copper-based nanomaterials and applications
- Magnetic Properties of Alloys
- Nanocluster Synthesis and Applications
- Magnetic Properties and Synthesis of Ferrites
- Chalcogenide Semiconductor Thin Films
Laboratoire National des Champs Magnétiques Intenses
2015-2024
Université Grenoble Alpes
2013-2024
Centre National de la Recherche Scientifique
2011-2022
Institut National des Sciences Appliquées de Toulouse
2018-2022
Université Toulouse III - Paul Sabatier
2017-2021
Université Joseph Fourier
1997-2016
Leiden University
2016
Laboratoire de Spectrométrie Ionique et Moléculaire
2007-2009
Laboratoire Interdisciplinaire de Physique
2004
Iowa State University
1999-2001
Abstract The pseudogap regime of high-temperature cuprates harbours diverse manifestations electronic ordering whose exact nature and universality remain debated. Here, we show that the short-ranged charge order recently reported in normal state YBa 2 Cu 3 O y corresponds to a truly static modulation density. We also this impacts on most properties, it appears jointly with intra-unit-cell nematic, but not magnetic, order, exhibits differences density wave observed at lower temperatures high...
We report on ${}^{63}\mathrm{Cu}$ NMR spectra, ${T}_{1}$ and ${T}_{2G}$ measurements in single crystals of underdoped, three-layered, ${\mathrm{HgBa}}_{2}{\mathrm{Ca}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{8+\ensuremath{\delta}}$, with ${T}_{c}\ensuremath{\simeq}115\mathrm{K}$. show clear evidence for the opening a spin gap below ${T}^{*}\ensuremath{\simeq}230\mathrm{K}$, highest temperature reported so far. Also, characteristic energy fluctuations is found to be higher than...
Our measurements of the ^{59}Co NMR spin-spin relaxation in URh_{0.9}Co_{0.1}Ge reveal a divergence electronic spin fluctuations vicinity field-induced quantum critical point at H_{R}≈13 T, around which reentrant superconductivity (RSC) occurs ferromagnetic heavy fermion compound URhGe. We map out strength (H_{b},H_{c}) plane magnetic field components and show that develop same limited region near H_{R} as where RSC is observed. This strongly suggests these pairing glue responsible for RSC....
We present an extensive NMR study of the spin-1/2 antiferromagnetic Heisenberg ladder Cu2(C5H12N2)2Cl4 in a magnetic field range 4.5 - 16.7 T. By measuring proton relaxation rate 1/T_1 and varying around critical H_c1 = Delta / g\mu_B 7.5 T, we have studied transition from gapped spin liquid ground state to gapless regime which can be described as Luttinger liquid. identify intermediate T > |H-H_c1|, where dynamics is (possibly) only controlled by T=0 point H_c1.
A 63Cu and 139La NMR/NQR study of superconducting (Tc=7 K) La1.94Sr0.06CuO4 single crystal is reported. Coexistence spin-glass phases found below ~5 K from NMR relaxation. spectra show that, upon cooling, CuO2 planes progressively separate into two magnetic phases, one them having enhanced antiferromagnetic correlations. These results establish the AF-cluster nature spin-glass. We discuss how this phase can be related to microsegregation mobile holes possible pinning charge-stripes.
We report on ${}^{139}\mathrm{La}$ and ${}^{63}\mathrm{Cu}$ NMR/NQR measurements in the high-${T}_{c}$ superconductor ${\mathrm{La}}_{1.90}{\mathrm{Sr}}_{0.10}{\mathrm{CuO}}_{4},$ with ${T}_{c}=26.5$ K. Spin fluctuations probed by spin-lattice relaxation ${(T}_{1})$ continuously slow down cooling through ${T}_{c}.$ argue that spin freezing superconductivity are bulk effects this sample. Thus both phenomena have to coexist microscopically. The distribution of ${T}_{1}$ values at low...
High ${T}_{c}$ superconductivity in ${\text{La}}_{2\ensuremath{-}x}{\text{Sr}}_{x}{\text{CuO}}_{4}$ coexists with (striped and glassy) magnetic order. Here, we report NMR measurements of the $^{139}\text{L}\text{a}$ spin-lattice relaxation, which displays a stretched-exponential time dependence, both pure disordered $x=0.12$ single crystals. An analysis terms distribution relaxation rates ${^{139}T}_{1}^{\ensuremath{-}1}$ indicates that: (i) spin-freezing temperature is spatially...
We report on $^{75}$As-NMR measurements in single crystalline BaFe$_{2}$(As$_{0.96}$P$_{0.04}$)$_{2}$ for magnetic fields parallel to the orthorhombic $[110]_{\rm o}$ and $[100]_{\rm directions above structural transition temperature $T_{\rm S}\simeq121$ K. A large difference linewidth between two field reveals in-plane anisotropy of electric gradient, even tetragonal phase. This provides microscopic evidence population imbalance As-$4p_{x}$ $4p_{y}$ orbitals, which reaches...
We present a detailed study of the temperature ($T$) and magnetic field ($H$) dependence electronic density states (DOS) at Fermi level, as deduced from specific heat Knight shift measurements in underdoped ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}$. find that DOS becomes independent above characteristic ${H}_{\mathrm{DOS}}$, ${H}_{\mathrm{DOS}}(T)$ line displays an unusual inflection near onset long-range 3D charge-density wave order. The $S$ shape is suggestive two mutually...
In order to identify the mechanism responsible for formation of charge-density waves (CDW) in cuprate superconductors, it is important understand which aspects CDW's microscopic structure are generic and material-dependent. Here, we show that, at local scale probed by NMR, long-range CDW YBa2Cu3Oy unidirectional with a commensurate period three unit cells (lambda = 3b), implying that incommensurability found X-ray scattering ensured phase slips (discommensurations). Furthermore, NMR spectra...
The proton nuclear spin-lattice relaxation rate 1/T1 has been measured as a function of temperature and magnetic field (up to 15 T) in the molecular ring Fe10. Striking enhancement is observed around values corresponding crossing between ground state excited states molecule. We propose that this due cross-relaxation effect Zeeman reservoir levels This provides powerful tool investigate quantum dynamical phenomena at level crossing.
We review NMR and NQR studies m trie normal state of high-Tc superconducting cuprates.Emphasis is given on the three major contributions brought by these techniques: presence antiferromagnetic fluctuations, possible justification a single spin fluid model, opening pseudogap in excitations for underdoped compounds.Some recent developments are addressed compared to theoretical models.In particular, quantitative analysis nuclear relaxation detailed ~~Cu, ~~Y ~~O nuclei, enabling companson with...
A 59Co NMR study of CoO2, the x=0 end member AxCoO2 (A=Na,Li,...) cobaltates, reveals a metallic ground state, though with clear signs strong electron correlations: low-energy spin fluctuations develop at wave vectors q not equal to 0 and crossover Fermi-liquid regime occurs below characteristic temperature T* approximately 7 K. Despite some uncertainty over exact cobalt oxidation state in this material, results show that electronic correlations are revealed as x is reduced 0.3. The data...
In Ba(Fe0.95Co0.05)2As2 all of the 75As NMR intensity at paramagnetic resonance position vanishes abruptly below Tonset(SDW)=56 K, indicating that magnetic (spin density wave) order is present in sample volume, despite bulk superconductivity Tc=15 K. The two phases thus coexist homogeneously microscopic scale. Ba0.6K0.4Fe2As2, on other hand, signal loss Tonset(SDW)~75 K not complete, revealing bound to finite-size areas sample, while remaining shows a clear superconducting response Tc=37...
The value of the upper critical field Hc2, a fundamental characteristic superconducting state, has been subject to strong controversy in high-Tc copper-oxides. Since issue tackled almost exclusively by macroscopic techniques so far, there is clear need for local-probe measurements. Here, we use 17O NMR measure spin susceptibility $\chi_{spin}$ CuO2 planes at low temperature charge ordered YBa2Cu3Oy. We find that increases (most likely linearly) with magnetic H and saturates above values...
The ${}^{1}\mathrm{H}$ hyperfine shift $K$ and NMR relaxation rate ${T}_{1}^{\ensuremath{-}1}$ have been measured as a function of temperature in the $S\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1/2$ Heisenberg antiferromagnetic ladder compound ${\mathrm{Cu}}_{2}({\mathrm{C}}_{5}{\mathrm{H}}_{12}{\mathrm{N}}_{2}{)}_{2}{\mathrm{Cl}}_{4}$. presence spin gap $\ensuremath{\Delta}\ensuremath{\simeq}{J}_{\ensuremath{\perp}}{\ensuremath{-}J}_{\ensuremath{\parallel}}$ this strongly coupled (...
Heat capacity (C), magnetic torque, and proton NMR relaxation rate (1/T(1)) measurements were performed on Fe6:Li single crystals in order to study the crossings between S = 0 1 2 states of molecular rings, at fields B(c1) 11.7 T B(c2) 22.4 T, respectively. C vs B data 0.78 K show that energy gap two remains finite B(c)'s (Delta(1)/k(B) 0.86 Delta(2)/k(B) 2.36 K) thus proving levels repel each other. The large Delta(1) value may also explain anomalously width peak 1/T(1) B, around B(c1)....