B. Kundys

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.

Multiferroicity and hydrogen-bond ordering in (C2H5NH3)2CuCl4 featuring dominant ferromagnetic interactions

We demonstrate that ethylammonium copper chloride, (C2H5NH3)2CuCl4, a member of the hybrid perovskite family is an electrically polar and magnetic compound with dielectric anomaly around the Curie point (247 K). We have found large spontaneous electric polarization below this point accompanied with a color change in the sample. The system is also ferroelectric, with large remnant polarization (37??C/cm2) that is comparable to classical ferroelectric compounds. The results are ascribed to hydrogen-bond ordering of the organic chains. The coexistence of ferroelectricity and dominant ferromagnetic interactions allows to relate the sample to a rare group of magnetic multiferroic compounds. In such hybrid perovskites the underlying hydrogen bonding of easily tunable organic building blocks in combination with the 3d transition-metal layers offers an emerging pathway to engineer multifuctional multiferroics.

Periodicity dependence of the ferroelectric properties in BiFeO3∕SrTiO3 multiferroic superlattices

Artificial superlattices of (BiFeO3)m(SrTiO3)m (m=1–10 unit cells) consisting of multiferroic BiFeO3 and insulating SrTiO3 layers were fabricated on (100)-oriented SrTiO3 substrates by pulsed laser ablation. The remnant polarization and leakage current behavior of these films were studied by varying the periodicity (8–80A) of the superlattice. Compared to single layer BiFeO3 thin films, the leakage current was reduced by a few orders of magnitude on increasing the periodicity. Reduced leakage and intrinsic polarization hysteresis were observed and confirmed by pulsed polarization analysis for all periodicities (∼20–60A). The leakage current was dominated by space charge limited conduction.

Multiferroicity with high-TC in ceramics of the YBaCuFeO5 ordered perovskite

A dielectric anomaly has been found near the incommensurate to commensurate antiferromagnetic phase transition (TN2≈230 K) in YBaCuFeO5 ceramics, a compound which crystallizes in an ordered perovskite structure. The existence of electric polarization below TN2 suggests the magnetism induced charge polarization effect that is also confirmed by its strong magnetic field dependence below TN2. Accordingly, the peak near TN2 of the magnetodielectric effect indicates a maximum of magnetodielectric susceptibility near the spin reorientation transition. Considering the abundance of magnetic compounds which structures derive from the perovskite, these results might open up the way toward the control of electric polarization near room temperature.A dielectric anomaly has been found near the incommensurate to commensurate antiferromagnetic phase transition (TN2=230 K) in YBaCuFeO5 ceramics, a compound which crystallizes in an ordered perovskite structure. The existence of electric polarization below TN2 suggests the magnetism induced charge polarization effect that is also confirmed by its strong magnetic field dependence below TN2. Accordingly, the peak near TN2 of the magnetodielectric effect indicates a maximum of magnetodielectric susceptibility near the spin reorientation transition. Considering the abundance of magnetic compounds which structures derive from the perovskite, these results might open up the way toward the control of electric polarization near room temperature.

A multiferroic ceramic with perovskite structure: (La0.5Bi0.5)(Mn0.5Fe0.5)O3.09

An ABO3 perovskite multiferroic, where the B-site cation is responsible for the magnetic properties and the A-site cation with lone pair electron is responsible for the ferroelectric properties, was synthesized with the composition (La0.5Bi0.5)(Mn0.5Fe0.5)O3.09 at normal conditions. This oxide exhibits a ferromagnetic transition around 240 K with a well defined hysteresis loop, and a significant reversible remnant polarization below 67 K similar to ferroelectric behavior. The magnetic interaction is interpreted by the ferromagnetic Fe3+–O–Mn3+ and antiferromagnetic Fe3+(Mn3+)–O–Fe3+(Mn3+) interactions competed with each other, whereas the ferroelectricity is predominantly due to the polar nature introduced by the 6 s2 lone pair of Bi3+ cations.

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

The ferroelectric properties of

Ferromagnetism and magnetodielectric effect in insulating LaBiMn4∕3Co2∕3O6 thin films

{\text{MnWO}}_{4}

Interfacial contribution to the dielectric response in semiconducting LaBiMn4∕3Co2∕3O6

single crystal have been investigated. Despite a relatively low remanent polarization, we show that the sample is ferroelectric. The shape of the ferroelectric loop of

Effect of coupled ferroelectric and antiferromagnetic fluctuations on dielectric anomalies in spin induced multiferroics

{\text{MnWO}}_{4}

Dielectric catastrophe at the magnetic field induced insulator to metal transition in Pr1-xCaxMnO3(x = 0.30, 0.37) crystals

strongly depends on magnetic field and temperature. While its dependence does not directly correlate with the magnetocapacitance effect before the paraelectric transition, the effect of magnetic field on the ferroelectric polarization loop supports magnetoelectric coupling.