Florence Porcher

Florence Porcher
Atomic Energy and Alternative Energies Commission | CEA · Centre d'Etudes de Saclay

Ph. D. Hab.

About

114
Publications
13,987
Reads
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2,318
Citations
Additional affiliations
September 2008 - present
Atomic Energy and Alternative Energies Commission
Position
  • Researcher
September 1998 - present
University of Lorraine
Position
  • Professor (Assistant)
September 1998 - August 2008
University of Lorraine
Position
  • Professor (Assistant)

Publications

Publications (114)
Preprint
Full-text available
The Ca$_2$MnReO$_6$ double perovskite is a spin-orbit-assisted Mott insulator with exotic magnetic properties, including a largely non-collinear Mn$^{2+}$ spin arrangement and nearly orthogonal coupling between such spins and the much smaller Re $5d$ magnetic moments. Here, the electron-doped compound Ca$_{1.7}$Y$_{0.3}$MnReO$_6$ is investigated. N...
Article
We studied structural and magnetic phase transitions under applied pressure for the doped cobaltite La0.75Ba0.25CoO2.9. Neutron and x-ray diffraction experiments established the coexistence of rhombohedral and cubic phases in the sample. The magnetic state at 2 K is best described as a long-range ordered antiferromagnet (AFM) with small ferromagnet...
Article
Full-text available
Indium-substituted strontium hexaferrites were prepared by the conventional solid-phase reaction method. Neutron diffraction patterns were obtained at room temperature and analyzed using the Rietveld methods. A linear dependence of the unit cell parameters is found. In3+ cations are located mainly in octahedral positions of 4fVI and 12 k. The avera...
Article
The local crystal/magnetic structures of the SrFe12−xInxO19 solid solutions (x= 0.1; 0.3; 0.6 and 1.2) were investigated using neutron powder diffraction. The measurements of the electric polarization for all investigated samples were carried out as a function of the external electric field. The presence of the ferroelectric and ferromagnetic order...
Article
Full-text available
The structural investigations of SrFe11.9In0.1O19 compound synthesized by solid-state method have been carried by neutron diffraction method in a wide temperature range. The appearace of spontaneous polarization that coexists with ferrimagnetic ordering has been found out at room temperature in strontium hexaferrite partially substituted with In io...
Article
The unconventional transport and magnetic properties of perovskitelike lanthanum cobalt oxide LaCoO 3 have been studied for more than five decades. This highly correlated electron system exhibits a variety of peculiar properties that are desirable for environmentally friendly energy solutions, fuel cell technologies, novel diesel engines, and oxyfu...
Article
Full-text available
The magnetic structure of Ca$_2$MnReO$_6$ double perovskite is investigated by neutron powder diffraction and bulk magnetization, showing dominant non-collinear Mn magnetic moments [$4.35(7)$ $\mu_B$] that are orthogonally aligned with the small Re moments [$0.22(4)$ $\mu_B$]. $Ab$-initio electronic structure calculations show that the strong spin-...
Article
In the framework of the crystal chemical investigation of Tetragonal Tungsten Bronze (TTB) niobates, the Ba2NdFeNb4-xTaxO15 solid solution has been investigated in order to gain insight on the relaxor to ferroelectric crossover and it features. Single-phase ceramics were synthesised by a conventional two-step firing and sintering and underwent exte...
Article
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Orbital ordering below 30 K was previously observed in the ferromagnetic YTiO3 compound both by polarized neutron diffraction (PND) and x-ray magnetic diffraction (XMD). In this paper we report a procedure for the joint refinement of a unique spin-density model based on both PND and XMD data. The distribution of the unpaired 3d electron of titanium...
Article
A new ground state of textbook compound strontium titanate (SrTiO3) is obtained by inducing a specific core-shell structure of the particles. Using a combination of high energy synchrotron and neutron diffraction, we demonstrate a lowering of the ferroelastic ground state towards a new antiferrodistortive phase, accompanied with strong shifts of th...
Article
Recently, RMn2O5 (R=rare earth, Bi, Y) type multiferroics have drawn considerable attention, because of magnetically induced ferroelectricity along with an extremely large magnetoelectric coupling. Here, we present a detailed study on NdMn2O5 which is a crucial composition between the nonferroelectric PrMn2O5 and ferroelectric SmMn2O5. We report th...
Article
Powders of the title compounds are prepared by solid state reactions of stoichiometric amounts of MnO, CuO, and WO3 (850 °C, 30 h) and by the citrate route from aqueous citric acid solutions of MnSO4, Cu(OAc)2, and (NH4)6[H2W12O40] (750 °C, 3 h).
Article
Polycrystalline samples of Mn1-xCuxWO4 (x ≤ 0.5) have been prepared by a solid-state synthesis as well as from a citrate synthesis at moderate temperature (850 °C). The goal is to study changes in the structural, magnetic, and dielectric properties of magnetoelectric type-II multiferroic MnWO4 caused by replacing Jahn-Teller-inactive Mn(2+) (d(5),...
Article
Full-text available
We have studied multiferroic YMn2O5 by high-pressure neutron diffraction in a large pressure range from 0.5 to 6.3 GPa. We observe a pressure-induced commensurate (PCM) phase with a propagation vector (1/2 0 1/2) that is different from those observed at ambient pressure. It coexists with the ambient pressure phases up to the highest pressure, with...
Article
Full-text available
We have studied the spin correlations with $\bf{k}$= ($\frac12$, $\frac12$, $\frac12$) propagation vector which appear below 0.4\, K in \tbti\ spin liquid by combining powder neutron diffraction and specific heat on Tb$_{2+x}$Ti$_{2-x}$O$_{7+y}$ samples with $x$=0, 0.01, -0.01. The $\bf{k}$= ($\frac12$, $\frac12$, $\frac12$) order clearly appears o...
Article
Spinel-type compounds of Fe–Ni–Sb–O system were synthesized as polycrystalline powders. The crystal and magnetic properties were investigated using X-ray and neutron powder diffraction, Mössbauer and X-ray absorption spectroscopy and magnetization measurements. The samples crystallize in the cubic system, space group Fd – 3 m. The distribution of c...
Article
We have studied the structural properties of industrial Zirconia Toughened Alumina (ZTA) composites for different compositions of zirconia and yttria at the main stages of the process. Influences on phases stability, lattice parameters, homogeneous and non-homogeneous strains, particles and crystallites sizes, have been considered and discussed. Th...
Article
Full-text available
Nanolamellar MAX phase compounds (Cr0.5V0.5)n+1AlCn are formed with n = 1, 2 and 3, and their 300 K structure is studied in detail by high-resolution neutron diffraction. While the n = 1 compound is found to have complete disordering of vanadium and chromium in the metallic layers, the n = 2 and 3 compounds show strong tendency for these elements’...
Article
Full-text available
Transparent polycrystalline ceramics present significant economical and functional advantages over single crystal materials for optical, communication, and laser technologies. To date, transparency in these ceramics is ensured either by an optical isotropy (i.e. cubic symmetry) or a nanometric crystallite size, and the main challenge remains to eli...
Article
We have studied the structural properties of industrial Zirconia Toughened Alumina (ZTA) composites for different compositions of zirconia and yttria at the main stages of the process. Influences on phases stability, lattice parameters, homogeneous and non-homogeneous strains, particles and crystallites sizes, have been considered and discussed. Th...
Article
The solubility of Ce in the La1-xCexSrGa3O7+δ and La1.54-xCexSr0.46Ga3O7.27+δ melilites was investigated, along with the thermal redox stability in air of these melilites and the conductivity variation associated with oxidization of Ce(3+) into Ce(4+). Under CO reducing atmosphere, the La in LaSrGa3O7 may be completely substituted by Ce to form the...
Article
Full-text available
We have studied the MnGe chiral magnet below T-N = 170 K, by magnetic measurements, Mossbauer spectroscopy, and by neutron diffraction at ambient and under nonhydrostatic pressure. At ambient pressure, we observe the coexistence of two magnetic phases belonging to the same crystal phase in a large temperature range (down to 100 K) below T-N: ferrom...
Article
Full-text available
The compound NdFe$_2$Al$_{10}$ ($Cmcm$, space group #63) has been studied by both powder and single-crystal neutron diffraction. Below T$_N$ = 3.9 K, the Nd$^{3+}$ magnetic moments order in a commensurate magnetic structure, whose unit cell consists of four orthorhombic unit cells stacked along the $b$ direction. It can be described either as doubl...
Article
Full-text available
The study, tailoring, and control of the coupling between magnetic layers triggered the development of spintronics and has been up to now focused on systems comprising at least one ferromagnetic layer. Here we present a system where two antiferromagnetic layers separated by an ultrathin tunnel barrier interact with each other. We have studied with...
Article
The structural and magnetic properties of γ-CoV2O6 low-dimensional magnetic oxide have been investigated with an emphasis on its magnetic structure. Our main results have been obtained by powder neutron diffraction measurements carried out under magnetic fields of 0, 0.52, and 1 T, corresponding to the antiferromagnetic, ferrimagnetic, and ferromag...
Article
High-resolution single crystal X-ray diffraction is used for the first time to obtain the charge density distribution in dehydrated Na-X zeolite. The electron density is extracted according to the Hansen & Coppens multipolar-model, from which Pval-κ-type atomic charges are derived. In order to compare the experimental electron density with theoreti...
Article
Full-text available
Cubic helimagnets such as MnSi and FeGe have provided paradigmatic cases of pressure-induced collapse of band ferromagnetism in metals, accompanied with exotic partial order and chiral spin textures. Isostructural MnGe stands out owing to its much shorter helix pitch and high magnetic moment. By combining resistivity, ac susceptibility, and neutron...
Article
New insight into the defect chemistry of the tetragonal tungsten bronze (TTB) Ba0.5-xTaO3-x is established here, which is shown to adapt to a continuous and extensive range of both cationic and anionic defect stoichiometries. The highly nonstoichiometric TTB Ba0.5-xTaO3-x (x = 0.25-0.325) compositions are stabilized via the interpolation of Ba(2+)...
Article
Structural properties and reversible deuterium uptake of MgD2-TiD2 nanocomposites have been studied by joint X-ray and neutron diffraction analyses to shed light on the extremely fast hydrogenation kinetics of these materials. (1-x)MgD2-xTiD2 nanocomposites with compositions ranging between x = 0 and 0.5 have been prepared by reactive ball milling...
Article
Within the series of ternary rare-earth transition metal carbides Sc3TC4 (T = Fe, Co, Ni) only the Co congener displays a structural phase transition at 72 K and an onset of bulk superconductivity at 4.5 K. In this paper we present the results of a detailed analysis of the structural, electronic, and vibrational properties of the low-temperature ph...
Article
Bismuth vanadate Bi4V2O(11-y) doped with Fe was studied by neutron diffraction. It was shown that Fe substitutes V only partially and the redundant iron forms an impurity hematite phase. In the sample with nominal content Bi 4 (V 0.96 Fe 0.04) 2 O 11Ày a new phase transition within the frame of the monoclinic structure with the appearing of inversi...
Article
The influence of the iron content on the magnetic, polar, and magnetoelectric properties of Ga 2−x Fe x O 3 (x = 1.0; x = 1.4) polycrystalline samples was studied by a combined magnetic (SQUID) and structural (X-ray and temperature-dependent neutrons diffraction) study. As ex-pected, the samples showed a ferrimagnetic structure, with moments aligne...
Article
Mn3Ga bulk material and thin films deposited on several different substrates have been investigated using x-ray and neutron diffraction, x-ray absorption spectroscopy, x-ray magnetic circular dichroism, and electronic structure calculations using density-functional theory with the aim of determining the atomic site occupancy, magnetic moments, and...
Article
On the basis of the Mn3+ for Fe3+ substitution in Pb2–xBaxFe2O5, a novel oxide Pb1.3Ba0.7MnFeO5 has been synthesized at normal pressure. Though it belongs to the same structural family, the mixed “MnFe” oxide exhibits a very different structural distortion of its framework compared to the pure “Fe2” oxide, due to the Jahn–Teller effect of Mn3+. Com...
Article
The red long-lasting luminescence properties of the ZnGa2O4:Cr3+ spinel material are shown to be much improved when germanium or tin is substituted to the nominal composition. The resulting Zn1+xGa2–2x(Ge/Sn)xO4 (0 ≤ x ≤ 0.5) spinel solid solutions synthesized here by a classic solid state method have been structurally characterized by X-ray and ne...
Article
Full-text available
Nanocrystalline PrCo(3) powder has been synthesized by high-energy milling and was subsequently annealed from 873 to 1273 K for 30 min to optimize the extrinsic properties. The structure and magnetic properties of the nanocrystalline PrCo(3) have been investigated by means of x-ray and neutron diffraction as well as magnetization measurements. All...
Article
Full-text available
A highly transparent polycrystalline BaAl4O7 ceramic is prepared by annealing a glass bead (obtained by melting a 1:2 molar mixture of BaCO3 and Al2O3 followed by rapid quenching) in an open-air atmosphere tubular furnace at 1000—1100 °C for 2—24 h.
Article
Nanoparticles of strontium titanate (SrTiO3) have been synthesized in the 15 nm to 1 μm size range and studied using a combination of dielectric, Raman, x-ray, and neutron measurements. When diminishing the grain size, a strong reduction of dielectric permittivity, an enhancement of (normally forbidden) Raman polar modes and a progressive decouplin...
Article
Full-text available
In this work, we investigate the magnetic properties of the monoclinic α-CoV2O6 by powder neutron diffraction measurements and ab initio calculations. An emphasis has been pointed towards the magnetic structure and the interaction between the Co ions leading to magnetic frustrations in this compound. Neutron diffraction experiments were carried out...
Article
Full-text available
Fully dense, transparent polycrystalline ceramics are simply obtained by direct and complete crystallization from glass. This is demonstrated for the previously unreported composition, BaAl(4) O(7) , which exhibits two orthorhombic polymorphs with micrometer grain size, both optically transparent in the visible range. This innovative synthetic rout...
Article
To some extent, rare-earth-doped UO(2) is representative of an irradiated nuclear fuel. The two phases we observed previously in neodymium-doped UO(2) are now interpreted as the existence of a miscibility gap in the U-Nd-O phase diagram using new results obtained with Raman spectroscopy. Extrapolating the miscibility gap in the U-Nd-O phase diagram...
Article
Solid solutions of (1-x)LaFeO3-(x)PbTiO3 (0<x<1) have been prepared by conventional solid-state reaction. These complex perovskites have been studied by means of X-ray (XRPD) and neutron powder (NPD) diffraction, complemented with dielectric, magnetic, heat capacity and M\"ossbauer measurements. Complete solubility in the perovskite series was demo...
Article
Full-text available
The search for durable dyes led several past civilizations to develop artificial pigments. Maya Blue (MB), manufactured in pre-Columbian Mesoamerica, is one of the best known examples of an organic-inorganic hybrid material. Its durability is due to the unique association of indigo molecule and palygorskite, a particular fibrous clay occurring in Y...
Article
Starting from the parent 10H-Ba(5)Co(5)X(1-x)O(13-δ) (trimeric strings of face-sharing CoO(6) octahedra with terminal CoO(4) tetrahedra, stacking sequence (chhch')(2)) and 6H-Ba(6)Co(6)X(1-x)O(16-δ) (similar with tetrameric strings, stacking sequence chhhch') hexagonal perovskites forms (X = F, Cl; c, h = [BaO(3)] layers ; h' = [BaOX(1-y)] layers),...
Article
Full-text available
The magnetic structure of cubic MnGe has been determined by powder neutron diffraction. MnGe has a helical spin structure with a propagation vector k=(0,0,ζ), where ζ=0.107(5) just below the transition temperature TN=170 K. The ζ value increases upon cooling and locks in to the value of 0.167(4) below 30 K. The moment value is 2.3(5)μB at 2 K. The...
Article
MnIn2O4 is prepared by the citrate method starting with stoichiometric amounts of In2O3 and MnCO3 dissolved in citric acid and HNO3.
Article
Two new compounds of composition Sr2FeMoO5.7N0.3 and Sr2FeMoO5N are prepared by annealing precursors obtained by the citrate route in flowing ammonia at 750 and 650 °C, respectively.
Article
The title compound has been synthesized by a citrate technique. The crystal structure has been investigated at room temperature from high-resolution neutron powder diffraction (NPD) data. It crystallizes in a cubic spinel structure, space group Fd (3) over barm, Z=8, with a=9.0008(1) angstrom at 295 K. It exhibits a crystallographic formula (Mn0.92...
Article
Full-text available
Nd(5)CoSi(2) was obtained from the elements by arc-melting followed by annealing at 883 K. Its investigation by single-crystal x-ray and neutron powder diffraction shows that this ternary silicide crystallizes as Nd(5)Si(3) in a tetragonal structure deriving from the Cr(5)B(3)-type (I4/mcm space group; a = 7.7472(2) and c = 13.5981(5) Å as unit cel...
Article
Full-text available
A polycrystalline sample of LuFe 2 O 4 has been investigated by means of powder synchrotron x-ray and neutron diffraction and transmission electron microscopy (TEM), along with Mössbauer spectroscopy and transport and magnetic properties. A monoclinic distortion is unambiguously evidenced, and the crystal structure is refined in the monoclinic C2/m...
Article
Full-text available
We have used a single SBA-15 silica batch (mesopore diameter of 7.1 nm) and the two-solvent impregnation technique with either pentane or cyclohexane to prepare model samples in which an initial aqueous solution of salt precursor (iron nitrate or iron chloride) is deposited mainly inside silica pores. Detailed characterization by SAXS, WAXS, Ar sor...
Article
Two new oxynitride double perovskites of composition Sr2FeMoO6−xNx (x=0.3, 1.0) have been synthesized by annealing precursor powders obtained by citrate techniques in flowing ammonia at 750 °C and 650 °C, respectively. The polycrystalline samples have been characterized by chemical analysis, x-ray and neutron diffraction (NPD), Mössbauer spectrosco...
Article
The title compounds have been synthesized by a citrate technique. The crystal structure of these materials has been studied at room temperature from high-resolution neutron powder diffraction data. In, Ru, and M=Mn,Fe are distributed at random over the metal sites of a C-M2O3 bixbyite-type structure, space group Ia3̄, with a=9.89000(3)Å for M=Mn an...
Article
Full-text available
This article presents the synthesis, structure determination, and structure analysis of alpha-La(2)WO(6). This high temperature polyrnorph Was directly observed using laboratory in situ high-temperature X-ray powder. diffraction and isolated at room temperature by rapid quenching from 1600 degrees C. Ab initio structure determination has been perfo...
Article
Full-text available
This work reports on the experimental investigation of wide band gap compounds LiMgZ (Z = P, As, Sb), which are promising candidates for opto-electronics and anode materials for lithium batteries. The compounds crystallize in the cubic (C1b) MgAgAs structure (space group ). The polycrystalline samples are synthesized by solid-state reaction method...
Article
Barium ruthenate Ba4Ru3O10, in which Ru3O12 trimers are connected together to form a checkered two-dimensional framework, has been synthesized and its structural, magnetic, and transport properties studied between 300 and 2 K. The paramagnetic to antiferromagnetic transition at TN ≈ 105 K evidenced on the susceptibility curve coincides with an incr...
Article
The diversification of antiferromagnetic (AFM) oxides with high Néel temperature is of fundamental as well as technical interest if one considers the need for robust AFM in the field of spin-tronics (exchange bias, multiferroics, etc.). Within the broad series of so-called hexagonal perovskites (HP), the existence of face-sharing octahedral units d...