Papers by Keyword: Magneto-Electric Effect

Abstract: Multiferroic composite films of (i) Co_0.6Zn_0.4Fe₂O₄(CZFO)-PbTi_0.7Zr_0.3O₃(PZT)-poly (vinylidene-fluoride)(PVDF) and (ii) Co_0.6Zn_0.4Fe₂O₄-BaTi_0.7Zr_0.3O₃(BZT)-PVDF were prepared by hot press method for magneto-dielectric studies. Different multiferroic composite films were named as CPT-1 (CZFO:PZT; 3:1) CPT-2 (CZFO:PZT; 3:2), CPT-3(CZFO:PZT; 3:3), CBT-1 (CZFO:BZT; 3:1), CBT-2 (CZFO:BZT; 3:2) and CBT-3 (CZFO:BZT 3:3). The entire composites were made with 70% ceramic and 30% wt. PVDF polymer. Line scanning by Scanning electron microscope (SEM) and Atomic force microscopy (AFM) images shows a homogeneous distribution of constituents in the composite film. It is observed that the dielectric permittivity (ε´) follows the MaxwellWagner model. Remnant polarization (P_r) and magnetocapacitance (MC) were found to vary with an applied magnetic field at room temperature. The absolute value of the magnetocapacitance (MC) was found higher for CBT-2 (MC ~ 0.79%) than for CBT-3 (MC ~ 0.57%) but lower than for CPT-3 (MC ~ 1.2%). A linear fit of the MC with M² yields the magnetoelectric quadratic coupling constant |γ| ~ 4.96 × 10^-6 for CBT-1, which is around 150 times lower than for CPT-1 (|γ| ~ 7.92 × 10^-4).

Abstract: The magnetic properties of an artificial multiferroic material, a Cr₂O₃/LiNbO₃/Cr₂O₃ hetero structure with various-thickness LiNbO₃ layers, were investigated. All samples showed ferromagnetism due to the existence of oxygen deficiency or an excess of the Cr₂O₃ layer in the LNO/Cr₂O₃ interface. The ferromagnetism of the samples was affected by the crystal orientation of the LiNbO₃ layer, and seemed to have a major impact on the magneto-electric behavior of this hetero system.

Abstract: We have investigated the relationships between the electric field-induced resistance change and the strength of the exchange interaction of the Cr2O3/ La0.7Sr0.3MnO3 (LSMO) magnetic hetero system. The hetero system subjected to field cooling (FC) showed a positive shift in the magnetization curves due to an exchange bias. The exchange bias field changed depending on the FC field. Resulting from the exchange behaviors, the resistance of LSMO film was changed by the application of an electric field to the Cr2O3 gate. This resistance change is more likely due to the interface interaction strength between the Cr2O3 and LSMO film

Abstract: We investigated the magnetic and dielectric properties of a metal (Pt)/insulator (Cr2O3)/semiconductor (Si) (MIS) capacitor composed of magneto-electric (ME) materials. The capacitor has anti-ferromagnetic properties and a very small electrically induced magnetic moment. It also shows capacitance-voltage (C-V) properties typical of a Si-MIS capacitor without any hysteresis. By inserting a thin Cr2O3-x layer, the C-V curve has a hysteresis window with a clockwise trace, which indicates that electrons have been injected into the Cr2O3-x layer. These results indicate that this MIS capacitor contains a floating gate and an ME insulating layer in a single system.

Abstract: The precursor powder of lead-zirconate-titanate (PZT) and NiFe2O4 (NFO) was prepared using one step sol-gel method. The dry powders got after a series of processes were sintered via a conventional ceramic solid-state reaction technique. All the diffraction peaks in the XRD patterns of the composites can be readily indexed to NFO and PZT, respectively. The SEM micrograph shows two different phases of PZT and NFO distinctly and the particle size of NFO was about 2~4 μm. The magnetoelectric (ME) coefficient, dielectric constant, piezoelectric constant, magnetic hysteresis loops of the samples were measured. The dc magnetic Hdc resulting in the maximum ME coefficient varies from 0.65kOe to 1.0kOe with the increase of the NFO volume fraction. The maximum magnetoelectric coefficient of 6.15Vcm-1Oe-1 was obtained at resonance frequency of 289.8kHz, dc magnetic intensity of 0.8kOe and NFO volume fraction of 0.25.

Abstract: Magnetic, dielectric properties and magnetoelectric effect of ceramics with a composition of 0.9 BaTiO3-0.1 LaMnO3 have been investigated. X-ray diffraction measurements showed that the sintered ceramics are composites containing a small amount of (La, Ba)MnO3 phase in the BaTiO3 matrix. These composites were multiferroic, having ferromagnetic and ferroelectric Curie temperatures of 330 K and 392 K respectively. We found that the composite sintered at 1150 °C exhibits a reduction of spontaneous magnetization as large as 55 % at room temperature when an electric field of 1.4 KV/mm is applied. This reduction is probably ascribed to a change of hole concentration distribution in the precipitated ferromagnetic (La, Ba)MnO3 and the resultant decrease of ferromagnetic Curie temperature.

Abstract: It is shown that in colossal magnetoresistance materials an inhomogeneous alternating magnetic field generates a strong electric field of non-inductive nature. This magnetoelectric effect is an analog of acoustoelectric effect in conventional semiconductors. Due to the above electric field spin waves in the former materials, like acoustic waves in the latter ones, acquire an additional attenuation at equilibrium. This attenuation may be converted to amplification by applying strong enough dc electric field drifting the carriers (solid-state Cherenkov’s effect). The experiments, which probed this phenomenon in HgCr2Se4 using spin wave pumping, are discussed.