Charles Simon

Magnetic field induced ferroelectric loop in Bi0.75Sr0.25FeO3−δ

Magnetic field induced ferroelectric hysteresis loop observed in Bi0.75Sr0.25FeO3−δ is of prime importance. The coexistence of antiferromagnetism and weak ferromagnetism is responsible for the original magnetoelastic and magnetoferroelectric properties. Upon external magnetic field application, the existence of a magnetostrictive effect supports a structural transition toward a homogeneous antiferromagnetic and ferroelectric phase. The magnetic field induced polarization is among the highest reported for BiFeO3 based systems in either thin film or bulk form (Pr=96μC∕cm2 at 10T) while the ferroelectric coercive field is among the lowest reported (Hc=661V∕cm at 10T). These properties make this material very attractive for technical applications.

Quantum entanglement of a large number of photons

A bipartite multiphoton entangled state is created through stimulated parametric down-conversion of strong laser pulses in a nonlinear crystal. It is shown how detectors that do not resolve the photon number can be used to analyze such multiphoton states. Entanglement of up to 12 photons is detected using both the positivity of the partially-transposed density matrix and a newly derived criteria. Furthermore, evidence is provided for entanglement of up to 100 photons. The multiparticle quantum state is such that even in the case of an overall photon collection and detection efficiency as low as a few percent, entanglement remains and can be detected.

Large Increase of the Curie Temperature by Orbital Ordering Control

Using first principle calculations we showed that the Curie temperature of manganites thin films can be increased by far more than an order of magnitude by applying appropriate strains. Our main breakthrough is that the control of the orbital ordering responsible for the spectacular T{C} increase cannot be imposed by the substrate only. Indeed, the strains, first applied by the substrate, need to be maintained over the growth direction by the alternation of the manganite layers with another appropriate material. Following these theoretical findings, we synthesized such superlattices and verified our theoretical predictions.

FeCr2O4 and CoCr2O4 spinels: Multiferroicity in the collinear magnetic state?

Dielectric permittivity (ɛ′) and electrical polarization (P) have been measured as a function of temperature for two polycrystalline ACr2O4 spinels (A = Fe and Co). Anomalies on the ɛ′(T) curves are detected at the characteristic magnetic transition temperatures (TC, TS, and Tlock-in) for FeCr2O4 and CoCr2O4 and also at the Jahn-Teller (JT) transition for FeCr2O4. The P(T) curves of both spinels exhibit transitions at TC showing that polar and ferrimagnetic states coexist in these oxides. The link between the distortion of the spinel structure due to the Jahn-Teller Fe2+ and the larger polarization value at 8 K, P = 35 μC/m2, against P = 3.5 μC/m2 for CoCr2O4, is also discussed.

Anomaly in the dielectric response at the charge-orbital-ordering transition of Pr 0.67 Ca 0.33 MnO 3

The complex impedance of a

Nonlinear effects and Joule heating in I-V curves in manganites

{\mathrm{Pr}}_{0.67}{\mathrm{Ca}}_{0.33}{\mathrm{MnO}}_{3}

UNUSUAL FIELD-DEPENDENCE OF THE REVERSIBLE MAGNETIZATION IN HEAVY-IONS IRRADIATED THALLIUM-BASED SINGLE-CRYSTALS

crystal has been measured. The frequency dependence is studied for a wide range of temperatures (50\char21{}403 K) and is found to be characteristic of relaxation process with a single Debye time relaxation constant, which is interpreted as a dielectric constant of the material. A strong peak is observed in this dielectric constant (up to

Frustration of Magnetic and Ferroelectric Long-Range Order in Bi2Mn4/3Ni2/3O6

{10}^{6})

Effect of magnetic field and temperature on the ferroelectric loop in MnWO 4

at the charge ordering transition suggesting an interpretation in terms of ordering electric dipoles at

Magnetodielectric coupling in a triangular Ising lattice : Experiment and modeling

{T}_{\mathrm{CO}}