Showing papers on "Magnetocapacitance published in 2021"
TL;DR: In this article, the phase transition and magneto-electric properties of a 70 wt. multiferroic composite have been studied and the maximum magnetoelectric coefficient of 26.78 mV/cm
Abstract: Here, we have studied the phase transition and magneto-electric properties of a 70 wt. % Pb(Fe0.5Nb0.5)O3–30 wt. % Co0.6Zn0.4Fe1.7Mn0.3O4 (70 wt. % PFN–30 wt. % CZFMO) multiferroic composite that exhibits a maximum magneto-electric (ME) coefficient of 26.78 mV/cm Oe at room temperature. Raman analysis confirms the formation of composite and development of strain with the shifting of Raman modes. The local symmetry breaking of end members of the composite is observed by the splitting of Raman modes. The first-order derivative of magnetization with temperature (dM/dT vs T) shows anomalies across 140 K due to the PFN phase, whereas the anomaly around 250 K is due to the spin glass transition of the CZFMO phase. The magnetization vs magnetic field (M–H) study at different temperatures reveals the existence of superparamagnetic behavior above 300 K. The temperature-dependent dielectric behavior of the composite shows an anomaly around ferroelectric phase transition (Tm) for the PFN phase along with the broad relaxation peak arising due to the CZFMO phase. The linear behavior of magnetocapacitance (MD%) with the square of magnetization (M2) suggests the existence of biquadratic ME coupling. The ME study on the composite suggests the existence of both direct and converse ME effects.
15 citations
TL;DR: In this paper, a series of NiFe2O4 (NFO) and Bi0.5TiO3 (BNT) ceramics were synthesized using the sol-gel method.
Abstract: Bi0.5Na0.5TiO3 (BNT) and NiFe2O4 (NFO) ceramics were synthesized using the sol–gel method. Further, a series of (1−x)BNT–xNFO (x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.25, 0.30, 1) magnetoelectric (ME) composites were prepared by microwave sintering. The composites phase purity and microstructure were investigated through X-ray diffraction and scanning electron microscope. The highest value of leakage current density was observed for 0.70BNT–0.30NFO, i.e., 3.77 × 10–5 A/cm2 at 5 kV/cm. Pure BNT showed higher dielectric constant (i.e., 576 at 1 kHz) at room temperature, which further decreases with NFO content. All composites showed ferromagnetic behavior. The direct and indirect ME coupling was examined by change in capacitance in an applied magnetic field. Giant magnetocapacitance was observed for 0.70BNT–0.30NFO, i.e., 27.51% at 1 kHz frequency. The quadratic–linear nature and higher-order ME coupling of composite samples have been computed using the Landau theory.
5 citations
24 Jun 2021
TL;DR: In this paper, a composite of perovskite PFN and magnetostrictive CZFMO material was used for spintronics applications, and the intrinsic magneto-electric coupling value for this composite was calculated to be 0.14 mVcm−1Oe−1, which is comparable to other typical multiferroic composites in bulk form.
Abstract: Multiferroic composites with enhanced magneto-electric coefficient are suitable candidates for various multifunctional devices. Here, we chose a particulate composite, which is the combination of multiferroic (PbFe0.5Nb0.5O3, PFN) as matrix and magnetostrictive (Co0.6Zn0.4Fe1.7Mn0.3O4, CZFMO) material as the dispersive phase. The X-ray diffraction analysis confirmed the formation of the composite having both perovskite PFN and magnetostrictive CZFMO phases. The scanning electron micrograph (SEM) showed dispersion of the CZFMO phase in the matrix of the PFN phase. The temperature-dependent magnetization curves suggested the transition arising due to PFN and CZFMO phase. The temperature-dependent dielectric study revealed a second-order ferroelectric to the paraelectric phase transition of the PFN phase in the composite with a small change in the transition temperature as compared to pure PFN. The magnetocapacitance (MC%) and magnetoimpedance (MI%) values (obtained from the magneto-dielectric study at room temperature (RT)) at 10 kHz were found to be 0.18% and 0.17% respectively. The intrinsic magneto-electric coupling value for this composite was calculated to be 0.14 mVcm−1Oe−1, which is comparable to other typical multiferroic composites in bulk form. The composite PFN-CZFMO exhibited a converse magneto-electric effect with a change in remanent magnetization value of −58.34% after electrical poling of the material. The obtained outcomes from the present study may be utilized in the understanding and development of new technologies of this composite for spintronics applications.
3 citations
TL;DR: In this article, the voltage dependence and frequency characteristics of TMC can be explained by the newly proposed Debye-Frohlich model using Zhang-sigmoid theory, parabolic barrier approximation, and spin-dependent drift diffusion model.
Abstract: Magnetic tunnel junctions (MTJs) in the field of spintronics have received enormous attention owing to their fascinating spin phenomena for fundamental physics and potential applications. MTJs exhibit a large tunnel magnetoresistance (TMR) at room temperature. However, TMR depends strongly on the bias voltage, which reduces the magnitude of TMR. On the other hand, tunnel magnetocapacitance (TMC), which has also been observed in MTJs, can be increased when subjecting to a biasing voltage, thus exhibiting one of the most interesting spin phenomena. Here we report a large voltage-induced TMC beyond 330% in MgO-based MTJs, which is the largest value ever reported for MTJs. The voltage dependence and frequency characteristics of TMC can be explained by the newly proposed Debye-Frohlich model using Zhang-sigmoid theory, parabolic barrier approximation, and spin-dependent drift diffusion model. Moreover, we predict that the voltage-induced TMC ratio could reach over 3000% in MTJs. It is a reality now that MTJs can be used as capacitors that are small in size, broadly ranged in frequencies and controllable by a voltage. Our theoretical and experimental findings provide a deeper understanding on the exact mechanism of voltage-induced AC spin transports in spintronic devices. Our research may open new avenues to the development of spintronics applications, such as highly sensitive magnetic sensors, high performance non-volatile memories, multi-functional spin logic devices, voltage controlled electronic components, and energy storage devices.
3 citations
TL;DR: In this article, the sign inversion phenomenon of tunnel magnetocapacitance was observed with frequency modulation and dc voltage application to MgO-based MTJ at room temperature.
Abstract: Tunnel magnetocapacitance (TMC) in magnetic tunnel junctions (MTJs) has recently attracted interest due to unique properties, such as large magnetic response, thermal stability, and robustness to the bias voltage. In this Letter, we report the sign inversion phenomenon of TMC observed with frequency modulation and dc voltage application to MgO-based MTJs at room temperature. A negative TMC is observed in the frequency region of about kHz due to the appearance of spin capacitance. By applying a dc voltage (a few hundred mV) in this frequency region, the spin flip is promoted in the parallel configuration of MTJs. This results in the observation of the sign inversion of TMC from negative to positive. These physical pictures can be well explained by the calculation based on the modified Debye-Frohlich model. Our research offers a deeper understanding of AC spin transports, DC spin accumulation, equilibrium and non-equilibrium spin dynamics.
2 citations
01 Jan 2021
TL;DR: In this article, the results revealed a strong magnetoelectric coupling between the ion-synthesized magnetic nanoparticles and the ferroelectric matrix, and the magnetocapacitance effects observed clearly in 3D ion-implanted plates of ferroelectric crystals.
Abstract: In this chapter, the recent works on the synthesis of nanocomposite materials obtained by nanosized inclusions of magnetic 3D metals in the surface layer of various ferroelectric crystals by using ion-beam implantation technique, and the results of investigations of magnetoelectric effects in these structures have been reviewed. Remarkable shifts of FMR lines have been observed on applying DC electrical field on the samples. These results revealed a strong magnetoelectric coupling between the ion-synthesized magnetic nanoparticles and the ferroelectric matrix. Another evidences of the magnetoelectric coupling are magnetocapacitance effects observed clearly in 3D ion-implanted plates of ferroelectric crystals. These studies showed that ion-beam synthesized nanocomposite layers of ferroelectrics reveal ferromagnetic properties and strong magnetoelectric effects that makes them useful for magnetoelectronics applications.
1 citations
TL;DR: In this article, the Nd1Bi2Fe5O12/Nd2Bi1Fe4Ga1O12 polycrystalline films on the glass substrate and the nd0.5Bi2.5
Abstract: The Nd1Bi2Fe5O12/Nd2Bi1Fe4Ga1O12 polycrystalline films on the glass substrate and the Nd0.5Bi2.5Fe5O12 epitaxial films on the single-crystal gadolinium gallium garnet substrate have been investigated by impedance and dielectric spectroscopy. The inductive contribution to the impedance and two relaxation channels related to ferroelectric domains and migration polarization have been established. The magnetocapacitance and magnetoimpedance have been determined. The conductive and polarization currents and the phase difference between them for the films of two types have been determined. The critical temperatures of the polarization disappearance and hysteresis I–V have been found. A model of the polarization caused by the piezoelectric effect and flexoelectric interaction has been proposed. I–V hysteresis is explained by the presence of ferroelectric domains near the interface and is associated with the hysteresis of the electric polarization.
1 citations
16 May 2021
TL;DR: In this article, the phase purity and microstructure of composite ceramics were analyzed through x-ray diffraction (XRD) pattern and scanning electron microscope (SEM) images.
Abstract: Lead-free magnetoelectric (ME) composites of (1-x) Bi 0.5 Na 0.5 TiO 3 – x Ni 0.5 Zn 0.5 Fe 2 O 4 (x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 1) were successfully synthesized by using sol-gel method. The phase purity and microstructure of composite ceramics were analyzed through x-ray diffraction (XRD) pattern and scanning electron microscope (SEM) images. The study of dielectric behavior reveals the insulating nature of composite ceramics. The highest value of dielectric constant (i.e. 532 at 1 kHz) and lowest tan δ (i.e. 0.07 at 1 kHz) was observed for x = 0. The dielectric constant decreases, whereas tan δ increases with NZFO concentration. The giant magnetocapacitance coefficient (MC %) was observed for x = 0.20 i.e. 27.48 % around 3 kOe at 1 kHz.
31 Mar 2021
TL;DR: In this article, the authors discuss three commonly used methods in multiferroic studies; the lock-in technique, the Sawyer-Tower (S-T) circuit and dielectric constant measurements.
Abstract: Magnetoelectric multiferroics are solid-state materials which exhibit a coupling between ferroelectric and magnetic orders. This phenomenon is known as the magnetoelectric (ME) effect. Multiferroic materials possess a wide range of potential applications in such fields as metrology, electronics, energy harvesting & conversion, and medicine. Multiferroic research is facing two main challenges. Firstly, scientists are continuously trying to obtain a material with sufficiently strong, room-temperature ME coupling that would enable its commercial application. Secondly, the measurement techniques used in multiferroic research are often problematic to implement in a laboratory setting and fail to yield reproducible results. The aim of the present work is to discuss three most commonly used methods in multiferroic studies; the lock-in technique, the Sawyer-Tower (S-T) circuit and dielectric constant measurements. The paper opens with a general description of multiferroics which is followed by mathematical representation of the ME effect. The main body deals with the description of the aforementioned measurement techniques. The article closes with a conclusion and outlook for future research.
TL;DR: Pb06Sr04TiO3/La07Sr03MnO3+La07Ca03MmO3-Si layer exhibits low resistivity and obvious negative magnetoresistivity (MR); the PST/LSMO/LCMO film shows notable magnetocapacitance (MC) above 350 K.
Abstract: Pb06Sr04TiO3/La07Sr03MnO3/La07Ca03MnO3 (PST/LSMO/LCMO) film is grown on Si substrate by chemical solution deposition method The film crystallizes perfectly into perovskite phases with a random crystalline orientation The La07Sr03MnO3/La07Ca03MnO3/Si layer exhibits low resistivity and obvious negative magnetoresistivity (MR); the PST/LSMO/LCMO film shows notable magnetocapacitance (MC) above 350 K, from 1029% to 295% Near room temperature, there is no distinguished magnetoelectric coupling; the MC is 343% @ 250 K, 295% @ 300 K and 328% @ 350 K respectively The mechanism can be explained in light of the Maxwell–Wagner (MW) model and the enhanced MR origin from the successive mixed manganite phases and spin dependent tunneling across the junctions of PST/LSMO/LCMO This work provides a new approach for designing and developing novel composites with promising MC
13 Sep 2021
TL;DR: In this article, the origin of magnetocapacitance effect in NiO prepared using solution combustion method was explored in the NiO powder showed formation of pure phase and the change in capacitance with applied magnetic field was of the order of 6.5 % at 1.2 MHz.
Abstract: The origin of magnetocapacitance effect in NiO prepared using solution combustion method was explored in this work. The structural analysis of NiO powder showed formation of pure phase. The change in capacitance with applied magnetic field was of the order of 6.5 % at 1.2 MHz. The positive sign of magnetocapacitance inferred that the process is interface mediated and supported by diminished magnetoresistance at the same frequency. The origin of this interface effect was explored using thermoluminescence study. The deconvolution of glow curve inferred formation of deep level defects with the number density of the order of 8.46 x 104 and activation energy or formation energy of 1.4 eV. The presence of deep level defects corroborated the observation of positive magnetocapacitance in NiO supporting the defect mediated change in capacitance.
TL;DR: In this article, a study of the capacitance of magnetic tunnel junctions with the tunneling magnetocapacitance (TMC) effect has drawn lots of attention, but there is still a lack of research on capacitance anisotropy.
TL;DR: In this article, the magnetoelectric coupling coefficient (αE 2 mV/cm-Oe) of single-phase BiFeO3 ceramic is denominated here, which is calculated by theoretical method (by using the numerical value of capacitance) in place of direct measurement of voltage.
Abstract: BiFeO3 is an attractive multiferroic ceramic for device application. The magnetoelectric coupling coefficient (αE ~ 2.2 mV/cm-Oe) of single-phase BiFeO3 ceramic is denominated here, which is calculated by theoretical method (by using the numerical value of capacitance) in place of direct measurement of voltage. An applied magnetic field raises the capacitance of the pellet of BiFeO3; analogous change in voltage gives the values of magnetoelectric coupling coefficient. Moreover, using the Ginzburg-Landau theory, the magnetoelectric interaction constant (γ) was calculated around ~ 9.3 × 10−1, which is numerically two times lower than the magnetoelectric coupling coefficient. This theoretical cum experimental study is very important in the view point of science and devices.