Gwilherm Nénert

Experimental evidence for an intermediate phase in the multiferroic YMnO3

We have studied YMnO3 by high-temperature synchrotron x-ray powder diffraction, and have carried out differential thermal analysis and dilatometry on a single crystal sample. These experiments show two phase transitions at about 1100 K and 1350 K, respectively. This demonstrates the existence of an intermediate phase between the room temperature ferroelectric and the high-temperature centrosymmetric phase. This study identifies for the first time the different high-temperature phase transitions in YMnO3.

Prediction for new magnetoelectric fluorides

We use symmetry considerations in order to predict new magnetoelectric fluorides. In addition to these magnetoelectric properties, we discuss which among these fluorides are the ones susceptible to present multiferroic properties. We emphasize that several materials exhibit ferromagnetic properties. This ferromagnetism should enhance the interplay between the magnetic and dielectric properties in these materials.

Observation of multiferroic properties in pyroxene NaFeGe2O6

We report the observation of multiferroicity in a clinopyroxene NaFeGe(2)O(6) polycrystal from the investigation of its electrical and magnetic properties. Following the previously known first magnetic transition at T(N1) = 13 K, a second magnetic transition appears at T(N2) = 11.8 K in the temperature dependence of the magnetization. A ferroelectric polarization starts to develop clearly at T(N2) rather than T(N1) and its magnitude increases up to ~13 μC m(-2) at 5 K, supporting the idea that the ferroelectric state in NaFeGe(2)O(6) stems from a helical spin order stabilized below T(N2). When a magnetic field of 90 kOe is applied, the electric polarization decreases to 9 μC m(-2) and T(N2) slightly increases by 0.5 K. At intermediate magnetic fields, around 28 and 78 kOe, anomalies in the magnetoelectric current, magnetoelectric susceptibility, and field derivative of magnetization curves are found, indicating field-induced spin-state transitions. Based on these electrical and magnetic properties, we provide a detailed low temperature phase diagram up to 90 kOe, and discuss the nature of each phase of NaFeGe(2)O(6).

Magnetoelectric and multiferroic properties of ternary copper chalcogenides Cu2MIIMIVS4

We investigate theoretically the ternary copper chalcogenides with the general formula Cu(2)M(II)M(IV)S(4). This family of compounds can crystallize in two different non-centrosymmetric structures, [Formula: see text] or Pnm 2(1). We show that all the reported members of Cu(2)M(II)M(IV)S(4) having the Pnm 2(1) symmetry exhibit a large spontaneous polarization. This result suggests that several of these materials are likely to be multiferroics since they order magnetically at low temperature. We discuss in detail in the framework of Landau theory the members Cu(2)MnSnS(4) and Cu(2)MnGeS(4) which should present both a linear magnetoelectric effect and multiferroic behavior.

Magnetic structure of the conductive triangular-lattice antiferromagnet PdCrO 2

We performed neutron single-crystal and synchrotron x-ray powder diffraction experiments in order to investigate the magnetic and crystal structures of the conductive layered triangular-lattice antiferromagnet PdCrO

Magnetic pyroxenes LiCrGe2O6 and LiCrSi2O6: Dimensionality crossover in a nonfrustrated S=3/2 Heisenberg model

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Magnetic structure and susceptibility ofCoSe2O5: An antiferromagnetic chain compound

with a putative spin chirality, which contributes to an unconventional anomalous Hall effect. We revealed that the ground-state magnetic structure is a commensurate and nearly coplanar 120

Weak ferrimagnetism and multiple magnetization reversal in α-Cr3(PO4)2

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Crystal structure and polymorphism of NaSrVO4: the first AIBIIXVO4 larnite-related structure from X-ray powder diffraction data

spin structure. The 120

Humidity-induced phase transitions of HEW lysozyme investigated by powder diffraction

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