A5101850812- Advanced Condensed Matter Physics
- Multiferroics and related materials
- Magnetic and transport properties of perovskites and related materials
- Physics of Superconductivity and Magnetism
- Ferroelectric and Piezoelectric Materials
- Nuclear materials and radiation effects
- High-pressure geophysics and materials
- Theoretical and Computational Physics
- Iron-based superconductors research
- Magnetism in coordination complexes
- Inorganic Fluorides and Related Compounds
- Quantum many-body systems
- Atomic and Subatomic Physics Research
- Organic and Molecular Conductors Research
- Perovskite Materials and Applications
- Rare-earth and actinide compounds
- Magnetic Properties of Alloys
- Magnetic properties of thin films
- Magneto-Optical Properties and Applications
- Nuclear Physics and Applications
- Solid-state spectroscopy and crystallography
- Advanced Thermoelectric Materials and Devices
- Advanced Semiconductor Detectors and Materials
- X-ray Diffraction in Crystallography
- Inorganic Chemistry and Materials
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2015-2024
CEA Paris-Saclay
2015-2024
Laboratoire Léon Brillouin
2014-2024
Centre National de la Recherche Scientifique
2015-2024
Université Paris-Saclay
2016-2024
Direction de la Recherche Fondamentale
2024
Paul Scherrer Institute
2023
CEA Paris-Saclay - Etablissement de Saclay
2008-2021
CEA Grenoble
2017
CEA Cadarache
2017
We have combined neutron scattering and piezoresponse force microscopy to show that the exchange field in CoFeB/BiFeO_{3} heterostructures scales with inverse of ferroelectric antiferromagnetic domain size BiFeO3 films, as expected from Malozemoff's model bias extended multiferroics. Accordingly, polarized reflectometry reveals presence uncompensated spins film at interface CoFeB. In view these results, we discuss possible strategies switch magnetization a ferromagnet by an electric using BiFeO3.
A previous study of the growth conditions has shown that single-phase BiFeO3 thin films can only be obtained in a narrow pressure–temperature window and these display weak magnetic moment. Here, we more detail structure magnetism by means reciprocal space mapping, Raman spectroscopy neutron diffraction. X-ray data suggest is tetragonal for 70 nm thick changes to monoclinic 240 films, thus remaining different from bulk (rhombohedral) structure. In monoclinically distorted film, diffraction...
We report the influence of epitaxial strain on multiferroic phase transitions BiFeO3 films. Using advanced characterization techniques and calculations we show that while magnetic Néel temperature hardly varies, ferroelectric Curie TC decreases dramatically with strain. This is in contrast behavior standard ferroelectrics where enhances polar cation shifts thus TC. argue this caused by an interplay oxygen tilting instabilities can drive both close together to yield increased magnetoelectric...
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...
We present an experimental study of the pyrochlore coumpound Nd2Zr2O7 by means neutron scattering and magnetization measurements down to 90 mK. The Nd$^{3+}$ magnetic moments exhibit a strong local $\langle$111$\rangle$ Ising anisotropy together with dipolar-octupolar nature, different from standard Kramers-doublet studied so far. show that, despite positive Curie-Weiss temperature, \ndzr\ undergoes transition around 285 mK towards all-in$-$all-out antiferromagnetic state. establish $(H,T)$...
Inelastic neutron scattering measurements have been performed on YMnO3, aiming to study the interplay between spin and lattice degrees of freedom in this hexagonal multiferroic material. Our provides evidence for a strong coupling magnons phonons, evidenced by opening gap below T(N) dispersion transverse acoustic phonon mode polarized along ferroelectric axis. The resulting upper branch is found lock one spin-wave modes. These findings are discussed terms possible hybridization two types...
The spin dynamics of the geometrically frustrated triangular antiferromagnet multiferroic CuCrO2 have been mapped out using inelastic neutron scattering. relevant Hamiltonian parameters modelling incommensurate modulated helicoid determined, and correspond to antiferromagnetic nearest next-nearest neighbour interactions in ab plane, with a strong planar anisotropy. weakly dispersive excitation along c reflects essentially two-dimensional character magnetic according classical energy...
We explore the spin dynamics emerging from N\'eel phase of chain compound antiferromagnet BaCo2V2O8. Our inelastic neutron scattering study reveals unconventional discrete excitations, so called Zeeman ladders, understood in terms spinon confinement, due to interchain attractive linear potential. These excitations consist two interlaced series modes, respectively with transverse and longitudinal polarization. The latter have no classical counterpart are related zero-point fluctuations that...
In this work, we show that the zero field excitation spectra in quantum spin ice candidate pyrochlore compound \ybti\ is a continuum characterized by very broad and almost flat dynamical response which extends up to $1-1.5$ meV, coexisting or not with quasi-elastic depending on wave-vector. The do evolve between 50 mK 2 K, indicating dynamics only little affected temperature both short-range correlated ordered regimes. Although classical simulations qualitatively capture some of experimental...
The magnetic ordering of the hexagonal multiferroic compound ${\text{YbMnO}}_{3}$ has been studied between 100 and 1.5 K by combining neutron powder diffraction, $^{170}\text{Y}\text{b}$ M\"ossbauer spectroscopy, magnetization measurements. Yb moments two crystallographic sites order at different temperatures: $4b$ site together with Mn (at ${T}_{N}\ensuremath{\simeq}85\text{ }\text{K}$) $2a$ well below 3.5 K). temperature dependences are explained within a molecular-field model, showing...
The pyrochlore compound Tb${}_{2}$Ti${}_{2}$O${}_{7}$ is known to remain in a spin-liquid state down the lowest attainable temperature (0.05 K), whereas current theories predict it should order into an antiferromagnetic structure. A number of models have been developed resolve this discrepancy, but none them could obtain ground state. We present here tentative explanation for lack magnetic based on presence Jahn-Teller-like distortion from local trigonal symmetry and physics two-singlet...
Low-energy magnon excitations in multiferroic BiFeO$_3$ were measured detail as a function of temperature around several Brillouin zone centers by inelastic neutron scattering experiments on single crystals. Unique features 1 meV are directly associated with the interplay Dzyaloshinskii-Moriya interaction and small single-ion anisotropy. The dependence these exchange interactions determined fitting dispersion spin-wave calculations. spectra best fits an easy-axis type magnetic anisotropy...
The dynamical magnetic correlations in ${\mathrm{Tb}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ have been investigated using polarized inelastic neutron scattering. Dispersive excitations are observed, emerging from pinch points reciprocal space and characterized by an anisotropic spectral weight. Anomalies the crystal field phonon excitation spectrum at Brillouin zone centers also reported. These findings suggest that Coulomb phases, although they present a disordered ground state with dipolar...
We present an experimental study of the quantum spin ice candidate pyrochlore coumpound \przr\ by means magnetization measurements, specific heat and neutron scattering up to 12 T down 60 mK. When field is applied along $[111]$ $[1\bar{1}0]$ directions, ${\bf k}=0$ induced structures settle in. find that ordered moment rises slowly, even at very low temperature, in agreement with macroscopic magnetization. Interestingly, for $H \parallel [1\bar{1}0]$, appears on so called $\alpha$ chains...
We have studied the low-energy spin dynamics between 4.6 and 0.07 K in a Tb${}_{2}$Ti${}_{2}$O${}_{7}$ single-crystal sample by means of inelastic neutron scattering experiments. The spectra consist dual response, with static an contribution, showing striking $Q$ dependencies. propose interpretation involving anisotropic exchange interaction combination breaking threefold symmetry at rare earth site. Simulations $Q$-dependent random phase approximation account well for response.
Examples of materials where an ``order by disorder'' mechanism is at play to select a particular ground state are scarce. It has recently been proposed, however, that the antiferromagnetic XY pyrochlore ${\mathrm{Er}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ reveals most convincing case this mechanism, with observation spin gap zone centers having interpreted as corroboration physics. Here we argue, anisotropy generated interaction-induced admixing between crystal-field and excited levels...
Conclusive evidence of order by disorder is scarce in real materials. Perhaps one the strongest cases presented has been for pyrochlore XY antiferromagnet ${\mathrm{Er}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$, with ground state selection proceeding induced through effects quantum fluctuations. This identification assumes smallness effect virtual crystal field fluctuations that could provide an alternative route to picking state. Here we show this not only significant, but competitive Further,...
Randomness in the arrangement of molecules within certain types frustrated magnets may offer a way to promote and stabilize exotic states matter known as spin liquids. New neutron-scattering experiments characterize disorder ice candidate Pr${}_{2}$Zr${}_{2}$O${}_{7}$ provide an explanation for some this material's unique properties.
Abstract In materials science, the substructure approach consists in imagining complex which a particular property is associated with distinct structural feature, so as to combine different chosen physical characteristics, otherwise have little chance coexist. Applied thermoelectric materials, it has been used achieve simultaneously phonon-glass and electron-crystal properties. Mostly studied for its superionic conductivity, AgCrSe 2 naturally layered compound, achieves very low thermal ~0.4...
Y${}_{3}$Cu${}_{9}$(OH)${}_{19}$Cl${}_{8}$, also known as Y-kapellasite, realizes an original anisotropic frustrated kagome model. Here, the authors study large phase-pure single crystals, obtained via external gradient method, by susceptibility, specific heat, thermal expansion, neutron scattering, and local $\ensuremath{\mu}$SR NMR techniques. These find subtle structural changes along with long-range magnetic ordering (1/3,1/3). Large quantum fluctuations reduce Cu${}^{2+}$ moments,...
Bi Fe O 3 thin films deposited on (111)-SrTiO3 substrates present both structural (rhombohedral) and multiferroic properties similar to bulk. The relaxation occurring when thickness increases the low critical possibly indicate different defect types distribution as compared (001)-BiFeO3, which may influence domain dynamics. same G-type antiferromagnetic order in bulk is observed by neutron diffraction, with a superimposed weak ferromagnetic moment (10emu∕cm3) showing planar anisotropy of...
We used polarized inelastic neutron-scattering measurements to shed light on the spin-lattice quantum entanglement in multiferroic materials. report an evidence for hybrid elementary excitations made of a mixing between spin waves and phonons, which can be considered as Goldstone modes. argue that Dzyaloshinskii-Moriya interaction could at origin this hybridization.