Observation Of Magnetoelectric Effect Research Articles

Observation of magnetoelectric effect in the S = 1/2 spin chain compound CoSe2O5 single crystal

The antiferromagnetic structure in the S = 1/2 zigzag spin chain compound CoSe2O5 was recently revealed by neutron scattering. Herein, we provide clear evidence for the linear ME coupling through systematic investigations on magnetic, dielectric, and ferroelectric properties. The simultaneous responses of the b-axis electric polarization (Pb) and dielectric anomaly (εb) against magnetic stimuli along the c-axis are revealed. In addition, both the ferroelectric transition and dielectric anomaly shift from the magnetic Néel temperature TN ∼ 8.5 K toward the low temperature under increasing H applied along the c-axis, providing clear evidence for the magnetism-driven ferroelectricity. The observed off diagonal linear ME effect is in accordance with the prediction based on ME tensor analysis for the magnetic space group Pb′cn. Consequently, our results may allow an interesting opportunity to further exploration of intriguing phenomena and physics of ferrotoroidicity in this linear-ME compound CoSe2O5 due to the existence of the off diagonal term in the ME tensor, similar to the case for LiCoPO4.

Observation of magnetoelectric effect in CuO-doped SrBi4Ti4O15 ceramics

Room temperature magnetoelectric coupling effect was observed in CuO-doped SrBi4Ti4O15 lead-free ferroelectric ceramics. Interstitial doping of CuO resulted in the formation of secondary phases at lower angles, which was confirmed from X-ray diffraction studies. Due to the strong magnetic superexchange interactions of CuO, weak room temperature ferromagnetic hysteresis curve was observed. The highest saturation magnetization of 1.61 memu/g and remnant polarization of 6.21 µC/cm2 was achieved for x = 1 mol% of CuO-doped ceramic. Further, the existence of weak magnetoelectric effect (χE = 0.1352 mVcm-1Oe-1) was also achieved. The obtained weak magnetoelectric effect is due to the presence of spontaneous magnetization and oxygen deficiency in the prepared samples.

Observation of magnetoelectric effects in a S=12 frustrated spin chain magnet SrCuTe2O6

The magnetoelectric effects are investigated in a cubic compound SrCuTe2O6, in which uniform Cu2+ (S = 1/2) spin chains with considerable spin frustration exhibit a concomitant antiferromagnetic transition and dielectric constant peak at TN ≈ 5.5 K. Pyroelectric Jp(T) and magnetoelectric current JME(H) measurements in the presence of a bias electric field are used to reveal that SrCuTe2O6 shows clear variations of Jp(T) across TN at constant magnetic fields. Furthermore, isothermal measurements of JME(H) also develop clear peaks at finite magnetic fields, of which traces are consistent with the spin-flop transitions observed in the magnetization studies. As a result, the anomalies observed in Jp(T) and JME(H) curves match well with the field-temperature phase diagram constructed from magnetization and dielectric constant measurements, demonstrating that SrCuTe2O6 is a new magnetoelectric compound with S = 1/2 spin chains.

Enhanced electrical properties and observation of magnetoelectric effect in the BiFeO3–BaTiO3/CoFe2O4 laminate composites

This work investigates the electrical, magnetic and magnetoelectric response of the BiFeO3–BaTiO3/CoFe2O4 laminate composite which was prepared by the conventional solid-state sintering method. The results show that 0.6BiFeO3–0.4BaTiO3 phase and CoFe2O4 phase can coexist without any obvious chemical reaction in the composites under high sintering temperature. Compared with the magnetoelectric particulate composites, the laminate composites exhibit better electrical and magnetoelectric properties due to their higher resistivity and lower leakage current. The magnetoelectric behaviors were dependent on the relative mass ratio of the two phases, the frequency and the magnetic field. The largest magnetoelectric coefficient of the laminate composites reaches up to 26.2mV/cmOe at a bias magnetic field of 400Oe and a frequency of 5kHz, which is three times as large as that of the particulate composites (8.5mV/cmOe).

First observation of magnetoelectric effect in M-type hexaferrite thin films

The magnetoelectric (ME) effect in M-type hexaferrite thin films is reported. Prior to this work, the ME effect in hexaferrite materials was observed only in bulk polycrystalline materials. Thin films of SrCo2Ti2Fe8O19 were grown on sapphire (0001) using pulsed laser deposition. The thin films were characterized by X-ray diffractometer, scanning electron microscope, energy-dispersive spectroscopy, vibrating sample magnetometer, and ferromagnetic resonance. We measured saturation magnetization of 1250 G, g-factor of 2.66, and coercive field of 20 Oe for these magnetoelectric M-type hexaferrite thin films. The magnetoelectric effect was confirmed by monitoring the change rate in remanence magnetization with the application of DC voltage at room temperature and it gave rise to changes in remanence in the order of 12.8% with the application of only 1 V (DC voltage). We deduced a magnetoelectric coupling, α, of 6.07 × 10−9 s m–1 in SrCo2Ti2Fe8O19 thin films.

Ultrathin oxide films and interfaces for electronics and spintronics

Oxides have become a key ingredient for new concepts of electronic devices. To a large extent, this is due to the profusion of new physics and novel functionalities arising from ultrathin oxide films and at oxide interfaces. We present here a perspective on selected topics within this vast field and focus on two main issues. The first part of this review is dedicated to the use of ultrathin films of insulating oxides as barriers for tunnel junctions. In addition to dielectric non-magnetic epitaxial barriers, which can produce tunneling magnetoresistances in excess of a few hundred percent, we pay special attention to the possibility of exploiting the multifunctional character of some oxides in order to realize ‘active’ tunnel barriers. In these, the conductance across the barrier is not only controlled by the bias voltage and/or the electrodes magnetic state, but also depends on the barrier ferroic state. Some examples include spin-filtering effects using ferro- and ferrimagnetic oxides, and the possibility of realizing hysteretic, multi-state junctions using ferroelectric barriers. The second part of this review is devoted to novel states appearing at oxide interfaces. Often completely different from those of the corresponding bulk materials, they bring about novel functionalities to be exploited in spintronics and electronics architectures. We review the main mechanisms responsible for these new properties (such as magnetic coupling, charge transfer and proximity effects) and summarize some of the most paradigmatic phenomena. These include the formation of high-mobility two-dimensional electron gases at the interface between insulators, the emergence of superconductivity (or ferromagnetism) at the interface between non-superconducting (or non-ferromagnetic) materials, the observation of magnetoelectric effects at magnetic/ferroelectric interfaces or the effects of the interplay and competing interactions at all-oxide ferromagnetic/superconducting interfaces. Finally, we link up the two reviewed research fields and emphasize that the tunneling geometry is particularly suited to probe novel interface effects at oxide barrier/electrode interfaces. We close by giving some directions toward tunneling devices exploiting novel oxide interfacial phenomena.

Structural analysis, magnetic properties and magnetoelectric effect in piezomagnetic–piezoelectric composites

The ferrite–ferroelectric composites of Ba 0.8Pb 0.2TiO 3 phase combined with different ferrite phases like CuFe 2O 4, CuFe 2− x Cr x O 4, and MnFe 2− x Cr x O 4 ( x indicates the molar fraction of the substituent's in the ferrite phase and varies as 0.2 and 0.4) were prepared by standard ceramic technique. The magnetoelectric (ME) effect in such composites is due to the strain induced in the ferrite phase by an applied magnetic field, which in turn gives rise to an electric voltage in the ferroelectric phase as a result of piezoelectric effect. The constituent phase, namely the ferrite phase being a driving force in the observation of ME effect, the effect of its variation is considered in the present communication. Structural characterization reveals that CuFe 2O 4 results in large distortion as compared to the other ferrites. The magnetic properties like ac susceptibility and hysteresis measurements reveal the existence of single domain particles in the composites of CuFe 2O 4 and Cu–Cr ferrites where as multidomain particles in the composites of Mn–Cr ferrites. The large value of magnetoelectric conversion factor (a measure of ME effect) is observed in the composites containing CuFe 2O 4. From this study it is concluded that the single domain particles of the ferrite phase together with large lattice distortion serve as better candidates in piezomagnetic effect and hence enhance the ME output.