Magnetocapacitance

About: Magnetocapacitance is a research topic. Over the lifetime, 497 publications have been published within this topic receiving 23846 citations.

Study of Structural, Magnetic, Dielectric Properties and Estimation of Magnetoeletric Coupling of La, Mn co-doped Bi 1−x La x Fe 0.97 Mn 0.03 O 3 Ceramics

Abstract: La and Mn co-doped Bi1−xLaxFe0.97Mn0.03O3 (BLFMOx, x = 0.05, 0.1, 0.2) ceramics were prepared by solid-state reaction method, and their structural, magnetic, dielectric and magnetocapacitance properties were studied. It was discovered that the co-substitution of La & Mn at sites of Bi & Fe suppressed impure phases which normally occur in BiFeO3 synthesis. BLFMOx samples were calcinated, and well crystalline phases were acquired at a sintering temperature of 950 °C. X-rays diffraction patterns of the samples were recorded and investigated for the affirmation of crystal structure and determination of the lattice parameters. The normal grain size of the samples was observed to be between 1 and 2 μm. M–H graphs of BiFeO3 and BLFMO0.05 ceramics consist of straight-line, confirming antiferromagnetic nature of samples. Dielectric constant was diminished with increase in frequency for each composition. BLFMOX ceramics showed negative magnetocapacitance and decrease in dielectric constant with magnetic field. Relative difference in dielectric constant initiated by external magnetic field might be approximated by ∆e/e = kM2 for BLFMOX, and here, magnetoelectric interaction (k) is negative.

Observation and theoretical calculations of voltage-induced large magnetocapacitance beyond 330% in MgO-based magnetic tunnel junctions.

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.

Magnetic and dielectric properties of A2CoSi2O7 (A=Ca, Sr, Ba) crystals

Abstract: We have investigated the magnetic and dielectric properties of $A_2$CoSi$_2$O$_7$ ($A$=Ca, Sr, and Ba) crystals with a two-dimensional network of CoO$_4$ and SiO$_4$ tetrahedra connected with each other through the corners. In Ca$_2$CoSi$_2$O$_7$, a weak ferromagnetic transition occurs at 5.7 K, where the dielectric constant parallel to the c axis shows a concomitant anomaly. The large magnetocapacitance effect is observed below 5.7 K; $\Delta \varepsilon (H)/\varepsilon (0) \equiv [\varepsilon (H)-\varepsilon (0)]/\varepsilon (0)$ reaches 13 % at 5.1 K\@. These results indicate a strong coupling between the magnetism and dielectricity in Ca$_2$CoSi$_2$O$_7$. Sr$_2$CoSi$_2$O$_7$ shows a similar magnetoelectric behavior to that of Ca$_2$CoSi$_2$O$_7$. In contrast, in Ba$_2$CoSi$_2$O$_7$, which has the different arrangement of SiO$_4$ and CoO$_4$ tetrahedra from that of Ca$_2$CoSi$_2$O$_7$, the magnetocapacitance is hardly observed. The key for the magnetocapacitance effect of $A_2$CoSi$_2$O$_7$ lies in the quasi-two-dimensional crystal structure.

Magnetocapacitance effect in core/shell NiO nanoparticles

Abstract: The exchange bias and magnetocapacitance properties of nickel oxide nanoparticles of average particle size 50 nm have been studied. NiO nanoparticles of uniform size distribution were synthesized by a sol-gel method using nickel acetate and polyvinyl acetate. The magnetic measurements show the ferromagnetic like behavior exhibiting exchange bias effect indicative of the formation of core/shell structure of NiO with a antiferromagnetic core and ferromagnetic shell. An electrical double layer capacitance behavior was observed for NiO nanoparticles in the cyclic voltammetry measurement, and it was found that the value of capacitance decreased by about 26 % under the application of magnetic field of 0.1 T.The exchange bias and magnetocapacitance properties of nickel oxide nanoparticles of average particle size 50 nm have been studied. NiO nanoparticles of uniform size distribution were synthesized by a sol-gel method using nickel acetate and polyvinyl acetate. The magnetic measurements show the ferromagnetic like behavior exhibiting exchange bias effect indicative of the formation of core/shell structure of NiO with a antiferromagnetic core and ferromagnetic shell. An electrical double layer capacitance behavior was observed for NiO nanoparticles in the cyclic voltammetry measurement, and it was found that the value of capacitance decreased by about 26 % under the application of magnetic field of 0.1 T.