Magnetocapacitance

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

Investigation of ferrimagnetism and ferroelectricity in AlxFe2−xO3 thin films

Abstract: AlxFe2−xO3 (x-AFO) thin films, belonging to the κ-Al2O3 family, are interesting because they show room temperature ferrimagnetism and have a polar crystal structure. These types of materials are being studied to observe simultaneous ferrimagnetism and ferroelectricity, and the possibility of coupling between the two. However, it is difficult to realise ferroelectric properties at room temperature, due to the low resistivity of the films. In this work, we have optimized the synthesis conditions to obtain x-AFO (0.5 ≤ x ≤ 1) thin films with high resistance. While magnetic measurements confirmed room temperature ferrimagnetism of the films, the maximum magnetization was observed for the composition x = 0.8. In addition, the Curie temperature was found to be influenced by oxygen pressure during deposition. Ferroelectric measurements on the films showed small remnant polarization (∼0.5–2 μC cm−2). In contrast, the predicted polarization from first principles calculations was calculated to be between 21 and 26 μC cm−2. The analysis also suggested that ferroelectric domain-switching occurs through shearing of in-plane oxygen layers. The presence of multiple in-plane domains, which oppose polarization switching of adjacent domains, is suggested to be the cause of the small observed polarization. The magnetocapacitance measurements showed weak magnetic coupling with the capacitance.

Investigation of physical properties of magnetoelectric LaFeO 3 -ErMnO 3 lead-free nanocomposites

Abstract: Magnetoelectric coupling has been investigated in lead-free nanocomposites of LaFeO3x–ErMnO3 (1−x) (x = 0.2 and 0.3) prepared by pyrophoric reaction process having piezomagnetic phase of LaFeO3 and piezoelectric phase of ErMnO3, while this nanocomposite reveals the signature of product property, i.e., Magnetoelectric coupling and magnetocapacitance effect (~ 50%) at room temperature attribute the enhancement of space charge polarisation of nanoparticles. Coexistence of both phases in nanocomposites is confirmed by X-ray diffraction technique. Electrical susceptibility corresponds to the domain wall motion due to electrostriction property. Temperature-dependent impedance analysis provides the evidence of space charge accumulation in nanocomposites exhibiting negative temperature coefficient resistance effect of the sample. The estimated activation energy from the Arrhenius fit suggests the hopping of carriers between La2+ and La3+ and Fe2+ and Fe3+ ions in the materials. The importance of the present study is the developing urge to know the details of magnetoelectric coupling and transport properties of a system for its technological applications.

Rapid preparation and magnetodielectric properties of trirutile Cr2WO6

Abstract: Dense pellets of > 99% purity trirutile Cr2WO6 were prepared in one step from starting oxides using spark plasma sintering, leading to simultaneous reaction and consolidation in 3 min at 1473 K. The reducing environment during processing may be partly responsible for the rapid reaction time in these oxides, with partial reduction of Cr3+ and the associated oxygen vacancies allowing rapid diffusion of cations. The low-temperature physical properties of Cr2WO6 were examined, and a new transition at T = 5.9 K was observed as an anomaly in the temperature-dependent dielectric permittivity and a corresponding anomaly in the specific heat. A strong enhancement of the magnetocapacitance is observed below this transition temperature at T = 5.9 K and may be associated with a change from collinear spin order to more complex spin order.

Interfacial contribution to magnetocapacitance in La0.05Tb0.95MnO3/La0.67Sr0.33MnO3/ SrTiO3 heterojunctions

Abstract: La005Tb095MnO3/La067Sr033MnO3/SrTiO3 heterojunctions were fabricated by laser molecular-beam epitaxy Dielectric properties as functions of temperature (77-320 K) and frequency (10(2)-10(6) Hz) of these junctions were investigated in detail The sample showed a notable magnetoresistive effect due to the contribution of the La067Sr033MnO3 layer and a diffuse dielectric anomaly which was found to arise from Maxwell-Wagner (MW) relaxation Both positive and negative magnetocapacitive behaviours were observed These behaviours were found to be intimately linked to the dielectric anomaly and can be well explained based on the combined role of the MW effect and magnetoresistance

Structural, Dielectric, Magnetic And Magnetoelectric Characterization Of Co0.5Ni0.5Fe2O4 - Bi0.9La0.1FeO3 Composite

Abstract: Mixed spinel -perovskite composites of (x) Co0.5Ni0.5Fe2O4-(1−x) Bi0.9La0.1FeO3(x = 0, 0.25, 0.40, 0.55, 1.0) have been synthesized by conventional solid state reaction method and annealed at 850 oC. The X-ray diffraction (XRD) pattern shows that the composites consisted of spinel Co0.5Ni0.5Fe2O4 and rhombohedral perovskite Bi0.9La0.1FeO3 ceramics. FESEM micrographs show closely packed microstructure with grain size in the range 503 nm - 960 nm. Variation of dielectric constant and dielectric loss with temperature at two fixed frequencies (500 kHz and 1 MHz) was studied. The composite with composition x = 0.55/sintered at 850 oC exhibits the largest coercitivity (Hc) of 883 Oe. The saturation magnetization (Ms) and magnetic moment (µB) increase with an increase of Co0.5Ni0.5Fe2O4 concentration in the composites. From ferroelectric hysteresis loop analysis the values of remnant polarization (Pr) and coercive field (Ec) was found to lie in the range of 0.0180.745 µC/cm 2 and 3.89-6.06 kV/cm. The relative change of magnetocapacitance was found to be 6.6% at a magnetic field of 8 kOe for x = 0.55 composition. Impedance analysis suggests the presence of a temperature dependent electrical relaxation in the material having a typical negative temperature coefficient of the resistance (NTCR) behavior analogous to a semiconductor. Copyright © 2015 VBRI Press.