Search

Bilayer thin films of GdFeO3/Fe97Si3 have been synthesized by RF–magnetron sputtering at different thicknesses of GdFeO3. A pure phase polycrystalline growth of GdFeO3 and Fe97Si3 has been confirmed by XRD measurements. Stress-induced room-temperature magnetocrystalline anisotropy has been confirmed in all the bilayer thin films. A high magnetic moment has been induced in antiferromagnetic GdFeO3 thin films resulting in the ferromagnetic character of all the samples. The ferromagnetic moment was found to be enhanced with increasing thickness of the GdFeO3 layer. The maximum value of the room- temperature magnetic moment has been observed as Ms ~ 9.3 emu/ml in 170-nm-thick GdFeO3 film. Dielectric measurements confirmed the induced magnetocapacitance due to grain boundary accumulation of charge carriers. Magnetic field control of capacitance and current–voltage measurements of these thin films represents a strong potential for the existence of magnetoelectric coupling in GdFeO3/Fe97Si3 films. A maximum 30% rise in magnetocapacitance and a 95.6% increase in tunneling current in an applied 1-kOe magnetic field was obtained for 170-nm-thick GFO thin film. These thin films possess applications in spintronic devices due to the presence of room- temperature magnetocrystalline anisotropy and magnetic control of the electric properties. [ABSTRACT FROM AUTHOR]

Magnetic capacitor, as a new type of device, has broad application prospects in fields such as magnetic field sensing, magnetic storage, magnetic field control, power electronics and so on. Traditional magnetic capacitors are mostly assembled by magnetic and capacitive materials. Magnetic capacitor made of a single material with intrinsic properties is very rare. This intrinsic property is magnetocapacitance (MC). The studies on MC effect have mainly focused on metal oxides so far. No study was reported in molecular materials. Herein, two complexes: (CETAB)2[CuCl4] (1) and (CETAB)2[CuBr4] (2) (CETAB=(2‐chloroethyl)trimethylammonium) are reported. There exist strong H−Br and Br−Br interactions and other weak interactions in complex 2, so the phase transition energy barrier is high, resulting in the widest thermal hysteresis loop on a molecular level to date. Furthermore, complexes 1 and 2 show large MC parameters of 0.247 and 1.614, respectively, which is the first time to observe MC effect in molecular material. [ABSTRACT FROM AUTHOR]

This paper presents the results of studies of the effects of magnetoresistance and magnetocapacitance in magnetic tunnel junctions Tb 2 2 − δ Co5 Fe 7 3 /Pr6 O 1 1 / Tb 1 9 − δ Co5 Fe 7 6 with perpendicular anisotropy of magnetic electrodes and a paramagnetic barrier layer. Experimentally measured values of tunnel magnetic resistance and tunnel magnetic capacitance in such contacts exceed 100% at room temperature. The paper analyzes the effect of magnetization reversal of one of the electrodes on the conductivity of magnetic tunnel junctions with electrodes that have perpendicular anisotropy. It is shown that significant changes in tunnel magnetic resistance and tunnel magnetic capacity in such contacts can be explained by the separation of electrons with major and minor spin polarization in the inverse nanolayer in the interface region. The separation of polarized electrons is caused by the magnetomotive force acting on the electron spin in a strongly gradient magnetic field. Such a magnetomotive force occurs with antiparallel magnetization of the magnetic electrodes and it has opposite directions for major and minor polarized electrons. As a result of the spatial separation of polarized electrons in the inversion layer, an inhomogeneous distribution of the electron density along the direction of magnetization of the magnetic contacts occurs. As a result, an additional Coulomb barrier between the magnetic electrodes and the dielectric nanolayer appears in the tunnel contacts and an additional spin capacitance appears. [ABSTRACT FROM AUTHOR]

Low field magnetocapacitance (MC) effect is studied in an inhomogeneous medium with ferromagnetic conducting and antiferromagnetic semiconducting content. The inhomogeneous medium was synthesized by solution combustion method with variation of fuel to oxidant ratio. Antiferromagnetic pure NiO and ferromagnetic Ni dispersed in NiO matrix were formed using single step combustion due to induced self-reduction in precursors. A crystallographic compression was observed in the NiO lattice with reduced Ni. The magnetocapacitance effect was evaluated in these, using relaxation analysis of the magneto-dielectric dispersion with modified Havriliak–Negami model. It was observed that the permittivity relaxation time was of the order of ~ 16 to 35 ms at 1.2 kOe in capacitors with magnetic content whereas in pure NiO it was of the order of ~ 65 μs. The analysis using macrospin approximation indicated dipole–dipole-like interaction or interface dominant MC of the order of + 7.5% at 1.2 kOe in pure NiO, whereas in Ni–NiO it was exchange mediated at higher frequencies and intermediate magnetic fields with – 4.15% MC at 1.2 kOe. The dominance of spin accumulation over spin dependent scattering was established by comparing MC with magnetoresistance (MR). The MR content was found to be of the order of ~ – 4% for capacitors with ferromagnetic component in the low field region indicating significant spin dependent scattering along with spin accumulation. Whereas in pure NiO the MR was of the order of – 0.6% indicating very low spin dependent scattering. AC reactance of the device was also evaluated to establish the interactions and strength of spin dependent scattering in these capacitors. The power analysis of magnetocapacitance indicated that Ni–NiO capacitors had coherent spin scattering with increased exchange mediated nonlinear, non-local interaction (long range) and magnetoelectric coupling whereas in NiO it was local interaction mediated by pronounced dipolar coupling. [ABSTRACT FROM AUTHOR]

Y-type hexaferrites possess multiple magnetic phases that are temperature and magnetic-field dependent. Some of these phases are ferrimagnetic and also exhibit room temperature spin-driven ferroelectricity that corresponds to a type-II magnetoelectric. The temperature stability and the magnetic activation field of the multiferroic phases of Y-type hexaferrite can be tuned by substituting Co2+ sites with transition metal ions, such as Ni2+. The present work describes a simple method for obtaining Y-type hexaferrites using high-energy ball milling with heat treatment at relative low temperatures, compared with other methods, and evaluates the effect of nickel as dopant in Ba 0.6 Sr 1.4 Co 2-x Ni x Fe 11 AlO 22 , with x varying from 0 to 2.0 (Δ x = 0.5), on the magnetic, dielectric, and magnetodielectric properties. The results show successful synthesis of pure hexagonal Y-type hexaferrite (R-3 m) by an easy and economical method. In addition, it is observed that nickel doping produces a diminution in the specific magnetization, a change in the magnetic thresholds of the magnetic phases, and an increase in space charge polarization. In addition, the magnetodielectric measurements also show different positive magnetocapacitance behaviors linked to the effect of doping on the magnetic and electronic structure. [ABSTRACT FROM AUTHOR]

Investigation on current conduction mechanism through Tb and Mn codoped Bismuth Ferrite grafted polyvinyl alcohol (BTFMO-PVA) nanocomposite film above room temperature (300 K – 415 K) is reported here in detail. A detailed study on dielectric properties of the sample is done over a wide temperature range in a frequency range of 20 Hz - 2MHz. The conduction is attributed to correlated barrier hopping model. Bipolaron hopping dominates over single-polaron hopping in this system. Complex electric modulus spectra and complex modulus spectra are well explained by suitable models to understand the effective dielectric response. The sample responds to the externally applied magnetic field exhibiting negative magnetocapacitance at room temperature.

Multiferroic behaviour in novel kind of ferroelectric (FE)–ferromagnetic (FM) particulate composites of (1−x)PbZr0.95Ti0.05O3(PZT)–(x)Ni0.7Zn0.3Fe2O4 (NZFO) [x = 0.1, 0.2, 0.3 and 0.4] has been studied. The study of FE–FM composites is represented in the context of structural, electrical, magnetic and magnetodielectric properties. X-ray diffraction reveals that both ferroelectric (PZT) and ferrite (NZFO) phases are present in prepared 0–3 type particulate composites. Scanning electron micrographs show the distribution of NZFO in the PZT matrix. Temperature-dependent relative permittivity studies revealed ferroelectric to paraelectric transition at ~ 250 °C. Room-temperature dielectric properties of the system have been studied in a wide range of frequencies (100 Hz to 1 MHz). Polarization versus electric field (P–E) studies at room temperature give conclusive confirmation of the presence of spontaneous polarization in all the composites. Magnetodielectric (MC%) measurements show the maximum 7.74% change at 1 kHz along with high values of magnetoelectric coupling coefficients γ ~ 5.98 × 10–5 (emu/g)−2, χE ~ 53.75 (mV/cm Oe) and χ ~ 16.60 × 10–8 (s/m) for 60PZT–40NZFO composite. [ABSTRACT FROM AUTHOR]

Multiferroic behaviour in novel kind of ferroelectric (FE)–ferromagnetic (FM) particulate composites of (1−x)PbZr0.95Ti0.05O3(PZT)–(x)Ni0.7Zn0.3Fe2O4 (NZFO) [x = 0.1, 0.2, 0.3 and 0.4] has been studied. The study of FE–FM composites is represented in the context of structural, electrical, magnetic and magnetodielectric properties. X-ray diffraction reveals that both ferroelectric (PZT) and ferrite (NZFO) phases are present in prepared 0–3 type particulate composites. Scanning electron micrographs show the distribution of NZFO in the PZT matrix. Temperature-dependent relative permittivity studies revealed ferroelectric to paraelectric transition at ~ 250 °C. Room-temperature dielectric properties of the system have been studied in a wide range of frequencies (100 Hz to 1 MHz). Polarization versus electric field (P–E) studies at room temperature give conclusive confirmation of the presence of spontaneous polarization in all the composites. Magnetodielectric (MC%) measurements show the maximum 7.74% change at 1 kHz along with high values of magnetoelectric coupling coefficients γ ~ 5.98 × 10–5 (emu/g)−2, χE ~ 53.75 (mV/cm Oe) and χ ~ 16.60 × 10–8 (s/m) for 60PZT–40NZFO composite. [ABSTRACT FROM AUTHOR]

A new type of graphene-based quantum Hall standards is tested for electrical quantum metrology applications at alternating current (ac) and direct current (dc). The devices are functionalized with Cr(CO)3 to control the charge carrier density and have branched Hall contacts based on NbTiN superconducting material. The work is an in-depth study about the characteristic capacitances and related losses in the ac regime of the devices and about their performance during precision resistance measurements at dc and ac. [ABSTRACT FROM AUTHOR]

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.

The permittivity of TmxMn1–xS (0 < x < 0.15) solid solutions is measured in the frequency range of 102–106 Hz at temperatures of 300–500 K in magnetic fields of up to 12 kOe. The migration and relaxation conductivity contributions to the electric polarization are established. The relaxation time and activation energy are calculated using the Debye model. A decrease in the capacitance and relaxation time in a magnetic field is observed. The electron polarization relaxation channel provided by recombination of the electron–hole pairs is found using the infrared spectroscopy investigations. [ABSTRACT FROM AUTHOR]

In this research, the (1-x)(BNKT-BST)-xBFTa ceramics were fabricated via a solid-state mixed oxide method and sintered at the temperature of 1125 °C for 2 h dwell time in order to obtain dense ceramics. The XRD and Raman data revealed the coexisting rhombohedral and tetragonal phases for all samples. The density increased with increasing the additive content, which resulted in the improvements of mechanical and dielectric properties. The maximum dielectric ("r = 1799) and mechanical properties (HV = 6.30 GPa, HK = 5.30 GPa, E = 97 GPa and KIC = 1.95 MPa.m1=2) were observed. The leakage current density (J) increased with increasing amount of the additive at high electric fields of 30 kV/cm while the resistivity (p) was also found to decrease with the additive. The magnetocapacitance (-MC%) value also increased with increasing of the additive. The obtained results suggested that the additive not only enhanced the mechanical but also improved electrical properties of the studied samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • Interface charge transfer takes place between LSMO and KNN-LTS layers. • (1 1 1)-oriented LSMO with highest out-of-plane lattice relaxation exhibit superior magnetic properties. • Higher MC in (1 1 1)-oriented sample than other samples near the T C of LSMO due to higher lattice relaxation. • (1 1 0)-oriented sample exhibit better MC performance at 300 K owing to its superior interface crystallization. • MC effect is found due to the interface ME coupling through charge transfer and MR effect in LSMO and it is tunable with orientation. We fabricated multiferroic heterostructures composed of La 0.67 Sr 0.33 MnO 3 (LSMO) and (K 0.48 Na 0.48 Li 0.04) (Nb 0.81 Ta 0.15 Sb 0.04)O 3 (KNN-LTS) on (0 0 1)-, (1 1 0)-, and (1 1 1)-oriented SrTiO 3 substrates using pulsed laser deposition technique. X-ray diffraction confirmed the coherent growth of LSMO layers, while KNN-LTS layers exhibited partial relaxation in the heterostructures, with relaxation increasing from (0 0 1) to (1 1 1) orientations. Notably, the (1 1 1)-oriented LSMO, which displayed the highest out-of-plane lattice relaxation, exhibited superior magnetic properties. On the other hand, (0 0 1)-oriented sample showcased the maximum ferroelectric and piezoelectric properties due to its high elastic deformation, whereas (1 1 1)-oriented sample, characterized by higher intrinsic lattice deformation, demonstrated better dielectric properties. Our elemental analysis confirmed interface charge transfer, indicating the presence of magnetoelectric coupling within the heterostructures. Then, the magnetocapacitance effect was attributed to a combination of interface magnetoelectric coupling and magnetoresistance in LSMO. The (1 1 1)-oriented sample displayed a remarkable MC value of approximately 62% near the transition temperature (around 352 K) of LSMO, while the (1 1 0)-oriented sample reached the highest MC of approximately 65% at 300 K. These findings suggest that engineered ferroelectric/ferromagnetic heterostructures hold promise for high MC performance at room temperature and offer opportunities for modulation with crystallographic orientation, making them potentially valuable for applications in multiferroic devices. [ABSTRACT FROM AUTHOR]

The mutual control of the electric and magnetic properties of a multiferroic solid is of fundamental and great technological importance. In this article, the synthesis procedure of La0.2Pb0.7Fe12O19 ceramics was briefly described and the data acquired for the materials characterization is presented. This data article is related to the research article-Acta Mater. 2016, 121, 144 (j.actamat.2016.08.083). Electric polarization hysteresis loop and I-V curve, which help to confirm the ferroelectricity of La0.2Pb0.7Fe12O19 ceramics, were presented. Strong magnetic polarization data was also presented. The great variation of the dielectric constants along with the magnetic field has been presented which helped to demonstrat the giant magnetocapacitance of La0.2Pb0.7Fe12O19. All the datasets were collected at room temperature. Large ferroelectricity, strong magnetism and colossal magneto-capacitance effect have been all realized in one single phase La0.2Pb0.7Fe12O19 at room temperature.

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 ∆ε/ε = kM2 for BLFMOX, and here, magnetoelectric interaction (k) is negative. [ABSTRACT FROM AUTHOR]

Magnetoelectric composites of xLaFeO3–(1 − x)Pb(Zr0.58Ti0.42)O3 (x = 0.2 and 0.3) have been prepared by pyrophoric reaction process. The observed room temperature magnetoelectric coefficient is enhanced with the increase of LaFeO3 content in nanocomposites. The maximum value of magnetoelectric coupling is found to be ∼1.5 mV/cm-Oe and ∼0.3 mV/cm-Oe, which may be due to the strain mediation of piezomagnetic phase and magnetodielectric property of the material. The frequency dependent AC conductivity at several temperatures indicates the thermally activated conduction process in the system. The electrical conductivity (both AC and DC) shows positive temperature coefficient resistance effect of the system where AC conductivity obeys Jonscher's power law. It demonstrates the hopping mechanism via small as well as large polaronic conduction process in the system. Maximum change of magnetoimpedance (∼185%) is observed at a frequency of 100 Hz at room temperature. The observed magnetoimpedance effect can be explained considering the skin effect. The magnetocapacitance effect shows the maximum value (∼60%) at lower frequency regime at room temperature attributing the evidence of Maxwell–Wagner interfacial or space charge polarization in the sample. At room temperature the magnetic field dependent capacitance of these samples is corroborating the evidence of magnetoelectric coupling. [ABSTRACT FROM AUTHOR]

Highlights • We suggests the possibility of enhanced magnetocapacitance under magnetic field. • We fabricated CoFe 2 O 4 /BaTiO 3 /CoFe 2 O 4 sandwich-type multilayered thin films by PLD. • With and without magnetic field, the electric potential and capacitance was changed. Abstract We studied on magnetoelectric behaviors of magnetically strained magnetostrictive materials-ferroelectric materials-magnetostrictive materials sandwich-type multilayered thin films. The sandwich-type multilayered thin films were deposited on Pt substrates by PLD system with a KrF excimer laser (λ = 248 nm). In particular, thin films were studied for their crystal structure and surface/interface microstructure as well as magnetic and electrical properties. The experimentally measured results have proved that saturated magnetizations (Ms) of CoFe 2 O 4 (20 nm, 20 nm, 200 nm)/BaTiO 3 (200 nm, 100 nm, 200 nm)/CoFe 2 O 4 (20 nm, 20 nm, 200 nm) sandwich-type multilayered thin films are measured as 23.58 emu/cm3, 38.52 emu/cm3, 103.71 emu/cm3 and the capacitance of those increased more under the magnetic field (1000 Oe) than zero field by 2.4%, 7.8%, 11.5% respectively. Our work suggests the possibility of enhanced magnetocapacitance under magnetic field by controlling the interfacial compressive/tensile stress of thin film. As a results we have compared the experimental and theoretical values depending on the parameters such as thickness and potential distribution of magnetostrictive materials through the simulation program COMSOL physics. [ABSTRACT FROM AUTHOR]

Abstract We investigate the electrical transport and dielectric properties of the nanocrystalline BaCo 0.9 Mn 0.1 O 3-δ under 2H- and 12H-type hexagonal phases. Temperature dependent electrical transport properties under 2H- and 12H-type phases show semiconducting-like behavior above the magnetic transition. The numerical value of electrical resistivity of the 12H-type phase at low temperature is 10-fold higher than the 2H-type counterpart, following the trend of structural stacking sequence. The 12H-type phase exhibits rarely known characteristics of ferromagnetic-insulator. The conduction mechanism under both phases is studied using variable range and small polaron hopping conduction mechanism. The 12H-phase shows large magnetoresistance (∼60%) under an application of 5 T of magnetic field at 50 K. The relation between magnetization and electrical resistivity around the magnetic ordering temperature is studied. The relation has been used to correlate the magnetic entropy change derived by magnetization and electrical resistivity measurements. Temperature dependence and magnetic field induced dielectric permittivity of the 2H- and 12H-type hexagonal phases is studied around the magnetic ordering temperature. Both phases exhibit dielectric suppression by magnetic ordering. The field dependence dielectric behavior shows magnetocapacitance value of ∼4% for 2H-phase and ∼94% for 12H-phase at their magnetic ordering temperature under external magnetic field of 5 T. The existence of intrinsic magneto-dielectric coupling is studied under the framework of Ginzburg-Landau theory for ferroelectromagnet. The origin of extrinsic magneto-dielectric contribution is justified using combinational effect of large negative magnetoresistance and Maxwell-Wagner effect. The magnetic and electrical transport properties of the nanocrystalline BaCo 0.9 Mn 0.1 O 3-δ compound are also studied using density of states. Nanocrystalline BaCo 0.9 Mn 0.1 O 3-δ sample shows novel magnetic field-induced effect on the magnetic, electric and dielectric properties around the same temperature window which could be utilized for multi-functional applications. Highlights • Electrical transport and dielectric properties of nanocrystalline BaCo 0.9 Mn 0.1 O 3-δ. • Relation between magnetic and electrical transport properties. • Study of physical properties using density of states (DOS) plots. • Magnetoresistance and magnetocapacitance properties. [ABSTRACT FROM AUTHOR]

Abstract The room temperature magnetoelectric properties of lead-free K 0.5 Na 0.5 NbO 3 (KNN) and CoFe 2 O 4 (CFO) particulate composites having general formula (1- x) KNN/ x CFO (where x = 0.1, 0.2, 0.3, 0.4 and 0.5)are presented here. Structural studies confirm the presence of phase pure KNN and CFO in the composites. Microstructural properties and grain size evaluations are carried out by using FESEM and TEM micrographs. The well-defined P-E and M-H hysteresis loops obtained for all the composites confirmed their multiferroic properties. The highest magnetocapacitance of 30% at a low frequency of 4 kHz and 5% at a high frequency of 100 kHz are noted for the composite with 40% CFO. Also, the composite with 40% CFO showed a maximum ME coupling coefficient of 28 mV/cm.Oe. The room temperature coupling properties and high magnetocapacitance at low frequencies make this non-lead-based ME nanocomposites as a promising candidate in the field of MEMS. [ABSTRACT FROM AUTHOR]

Highlights • Low temperature neutron diffraction data reveal non-collinear magnetic structure in Co 4 Ta 2 O 9. • Neutron diffraction data fit best to a non-centro-symmetric crystal structure below Neel temperature. • Correlation between magnetic structure and improper ferroelectricity is analyzed for Co 4 Ta 2 O 9. • Co-existing large magnetoelectric coupling is determined in the spin-flop phase of Co 4 Ta 2 O 9. Abstract We study magnetocapacitance (MC) effect and magnetoelectric (ME) coupling in spin-flop driven antiferromagnet Co 4 Ta 2 O 9. Powder neutron diffraction data reveal that the magnetic structure corresponds to a non-collinear arrangement along with a non-centrosymmetric crystal structure below Néel Temperature. Electric polarization is achieved below Néel temperature only when the sample is cooled in the presence of external magnetic field. The magnetocapacitance data at high magnetic fields are analyzed by phenomenological Ginzburg-landau theory of ferro-electromagnets and it is found that change in dielectric constant is proportional to the square of magnetization. The saturation polarization and magnetoelectric coupling are estimated to be 52 µC/m2 and γ = 1.4 × 10−3 (emu/g)−2 respectively at 6 Tesla. Strong magnetoelectric coupling and ferroelectric phase in the anti-ferromagnetic Co 4 Ta 2 O 9 are correlated to magnetic structure as derived from neutron diffraction data. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • 0.3NiFe 2 O 4 – 0.7BiFeO 3 nanocomposite has competing magnetic interactions and possible spin galss behaviour. • 0.3NiFe 2 O 4 – 0.7BiFeO 3 nanocomposite exhibit magnetocapacitance of 13.5% and 7.8% (at 5000 Oe) at room temperature. • 0.3NiFe 2 O 4 – 0.7BiFeO 3 nanocomposite exhibits spin glass freezing behaviour around 25 K. Abstract We report on magnetocapacitance, spin dynamics through AC succeptability measurements and dielectric anomalies in 0.3NiFe 2 O 4 – 0.7BiFeO 3 nanocomposite. Structural studies (purity and phase) and surface morphology of the 0.3NiFe 2 O 4 – 0.7BiFeO 3 nanocomposite were examined by X-ray diffraction (XRD), Raman Spectra, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). TEM and SEM images indicate the uniform distribution of nanoparticles in parent pahase as well as in the composite. Energy dispersive X-ray (EDX) analysis indicates the presence of Ni, Fe, O and Bi elements in 0.3NiFe 2 O 4 – 0.7BiFeO 3 nanocomposite. Magnetization measurements were performed at 300 K, 50 K and at 2 K and the Field Cooled (FC) and Zero Field Cooled (ZFC) measurements were carried out from 350 K to 2 K. ZFC and FC magnetization curves exhibit a hump around 30 K indicating the existence of competing magnetic interactions and possible spin galss behaviour. AC succeptibility measurements at various frequencies confirm the spin glass freezing behaviour of 0.3NiFe 2 O 4 – 0.7BiFeO 3 nanocomposite around 25 K with the relaxation time and activation energy in the order of 10−7 s and 0.938 meV respectively. The dielectric constant and dielectric loss at various frequencies and temperatures indicate the dielectric relaxation behaviour of 0.3NiFe 2 O 4 – 0.7BiFeO 3 nanocomposite. A rapid increase in the dielectric constant near the antiferromagnetic transition temperature (T N ∼ 643 K) of BiFeO 3 indicates the existence of magneto-electric coupling in this composite. Magnetocapacitance (MC) of 0.3NiFe 2 O 4 – 0.7BiFeO 3 composite was measured at room temperature and the MC values of 13.5% and 7.8% (at 5000 Oe) are observed when the pellet is perpendicular and parallel to the magneticfield direction respectively. The presented magnetic and dielectric studies reveal the existence of magnetoelectric coupling and spin glass frezing of 0.3NiFe 2 O 4 – 0.7BiFeO 3 nanocomposite. [ABSTRACT FROM AUTHOR]

Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

We report the observation of a magnetocapacitance effect at the interface between Ni and epitaxial nonpolar BiInO 3 thin films at room temperature. A detailed surface study using X-ray photoelectron spectroscopy (XPS) reveals the formation of an intermetallic Ni-Bi alloy at the Ni/BiInO 3 interface and a shift in the Bi 4f and In 3d core levels to higher binding energies with increasing Ni thickness. The latter infers band bending in BiInO 3 , corresponding to the formation of a p-type Schottky barrier. The current-voltage characteristics of the Ni/BiInO 3 /(Ba,Sr)RuO 3 /NdScO 3 (110) heterostructure show a significant dependence on the applied magnetic field and voltage cycling, which can be attributed to voltage-controlled band bending and spin-polarized charge accumulation in the vicinity of the Ni/BiInO 3 interface. The magnetocapacitance effect can be realized at room temperature without involving multiferroic materials.

Abstract Polycrystalline samples of Bi 0.9 Eu 0.1 FeO 3 , Bi 0.9 Gd 0.1 FeO 3 , and Bi 0.9 Eu 0.05 Gd 0.05 FeO 3 ceramics were synthesized by a solid-state reaction method, followed by rapid quenching to room temperature. Bi 0.9 Eu 0.1 FeO 3 shows higher magnetization than Bi 0.9 Gd 0.1 FeO 3 and Bi 0.9 Eu 0.05 Gd 0.05 FeO 3. This can be explained by lattice distortion, and the change in the statistical distribution of Fe3+/Fe2+. Similarly, ferroelectric polarization of Bi 0.9 Eu 0.1 FeO 3 was found to be higher than that of Bi 0.9 Gd 0.1 FeO 3 and Bi 0.9 Eu 0.05 Gd 0.05 FeO 3. However, the absolute value of the magnetocapacitance of Bi 0.9 Eu 0.05 Gd 0.05 FeO 3 (∼1.6%) was found to be higher than that of Bi 0.9 Eu 0.1 FeO 3 (∼1.3%) and Bi 0.9 Gd 0.1 FeO 3 (∼1.1%). In addition, the quadratic component of magnetoelectric coupling is higher for Bi 0.9 Eu 0.05 Gd 0.05 FeO 3 , which makes Bi 0.9 Eu 0.05 Gd 0.05 FeO 3 attractive for further study. Highlights • The dielectric constant at room temperature of sample-3 was found to be higher than that of samples-1 and 2. • The magnetization of sample-3 was found to be greater than that of samples-1 and 2. • The polarization–electric field loop of sample-3 was found to be better than that of samples-1 and 2. • The absolute value of the magnetocapacitance of sample-2 was found to be higher than that of sample s- 1 and 3. [ABSTRACT FROM AUTHOR]

Multiferroicity in perovskite-based ceramics is considered as a foundation of spintronics. Co-existence of two or more ferroic orders in single phase ceramics can be proclaimed as a redeemer for the energy related issues and key element in sensitive device applications. In this work, we report an appropriate magnetoresistive effect for the novel applications in sensing and recording under low magnetic field in BiFe 1-x Mn x O 3 with x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0, synthesised by sol-gel method. All the calcined samples exhibited crystalline texture; however, a gradual structural phase transition was evident with Mn-substitution at Fe-site in BiFeO 3 . The structural analysis revealed that the composition, BiFe .8 Mn .2 O 3 settles with the most stable rhombohedral crystal structure. A giant magnetoresistance effect under an applied magnetic field (up to 6 kOe) has been exhibited by this particular composition attributed to its stable rhombohedral structure. Complex impedance analysis depicted a wide range of applicable frequency suitable for sensing devices at room temperature. The impedance analysis and optimised magnetoresistive effects in Mn-substituted BiFeO 3 could help information technology by rectifying various issues relevant to sensing devices and energy losses in spintronics-based applications at room temperature. [ABSTRACT FROM AUTHOR]

The paper reports the synthesis of Ba 1-x Sr x TiO 3 (BSTx) for x = 0.20 and 0.30 via hydrothermal route followed by microwave sintering to result into the BST nano particles of size nearly 60 nm. The Co 0.9 Ni 0.1 Fe 2 O 4 (CNFO) is also synthesized using hydrothermal route to achieve Nano-crystalline particles. The composites yCNFO-(1-y)BST x with y = 0.2,0.3 & 0.4 and x = 0.2 and 0.3 are investigated for the variation of dielectric constant as a function of applied magnetic field (H) for the frequency between 100 Hz and 1 MHz. The maximum value of Magnetocapacitance (MC) is −6% for the 0.20CNFO-0.8BST 0.20 while the maximum value of Magnetoelectric Coefficient (α) is 5 mV/Oe.cm for the 0.20CNFO-0.8BST 0.30 . [ABSTRACT FROM AUTHOR]

Antiferromagnetic LuFeO 3 can be good multiferroic by having ferroelectricity in its non-centrosymmetric hexagonal phase. But, it is hard to stabilize this metastable phase, preventing the stable orthorhombic phase. In this work, metastable hexagonal LuFeO 3 (LFO) nanoparticle was stabilized in chemical sol-gel route in pure phase and co-doped with Co and Ti in the same route to synthesize Lu 0.9 Co 0.1 Fe 0.9 Ti 0.1 O 3 (LCFTO) nanoparticles. Room temperature multiferroicity of bare LFO was established through relevant characterization. And motive behind the co-doping is to enhance the magnetoelectric behavior of the bare system to synthesize a new monophasic type II magnetoelectric multiferroic. Structural investigation by thorough Rietveld analyses of the recorded X-ray diffractograms, confirmed the formation of pure hexagonal (P6 3 cm) phase of both bare and doped LFO. However, deviations in various structural & microstructural parameters were observed in the doped system, which is mainly responsible for the enhancement of magnetic and electric properties of the sample. Presence of antiferromagnetic transition at ∼604 K confirmed the room temperature magnetic ordering of bare LFO. Interestingly, LCFTO shows a drastic enhancement of magnetic property than the bare one in all concerns, where the maximum magnetization at the maximum applied field is enhanced by nearly 36 times at room temperature. Detailed high-temperature dielectric investigation shows, good dielectric strength (∼261) of LFO gets enhanced highly in LCFTO (∼1053) and a high relaxation time having negligible loss factor with an indication of ferro to paraelectric transition above room temperature. Current density vs. electric field (J-E) curve suggests the presence of polarization at room temperature with negligible leakage loss. Direct measurement of ferroelectric loop shows the ferroelectricity (P max ∼0.064 µc/cm2) of bare LFO at room temperature and a well improvement in the doped LCFTO (P max ∼0.151 µc/cm2). The presence of room temperature magnetoelectric coupling, confirmed by magnetocapacitance measurements, results in a high value (∼5 %) of magnetocapacitance in the doped system which is also much higher than the bare one (<∼1 %) as expected. All these properties confirm the magnetoelectric multiferroicity of bare h-LuFeO 3 at room temperature. And, co-doping in hexagonal LuFeO 3 nanoparticle system results in a considerable improvement in its magnetoelectric behavior, so this co-doped system can be a promising and potential magnetoelectric multiferroic for the future generation magnetoelectric devices. • Metastable hexagonal LuFeO 3 was stabilized in nano range in pure phase. • Room temperature magnetic ordering is established with high Néel temperature (∼ 604 K). • Room temperature magnetoelectric multiferroicity is established. • Multiferroicity highly enhanced by co-doping as Lu 0.9 Co 0.1 Fe 0.9 Ti 0.1 O 3 , having magnetocapacitance enhancement by ∼4.3 times. • Magnetic enhancement of ∼25 times, ferroelectric enhancement by 2.36 times was obtained at RT by co-doping. [ABSTRACT FROM AUTHOR]

• Bare and Co-Ti co-doped HoFeO 3 was synthesized in nano range in pure orthorhombic phase. • Room temperature magnetic ordering is established with high Néel temperature (∼637 K). • Maximum magnetizartion enhaced by 73% in HCFTO than HFO. • Dielectric constant enhanced to nearly double, ferroelectricity enhanced by 52.5% at RT by co-doping. • Multiferroicity highly enhanced by co-doping, having magnetocapacitance enhancement by ∼ 4.94 times. Nanocrystalline HoFeO 3 is a potential multiferroic and will be more useful if its multiferroicity can be enhanced by improving the magnetic and electric ordering. In this regard, co-doping with Co and Ti, was considered in HoFeO 3 (HFO) to enhance its magneto-electric behavior and thus synthesize a new monophasic multiferroic, Ho 0.95 Co 0.05 Fe 0.95 Ti 0.05 O 3 (HCFTO). Both the pristine and doped HFO nanoparticles were synthesized in sol–gel route. Rietveld analyses of X-ray diffractograms, confirmed the formation of pure orthorhombic (Pnma) phase of both bare and doped HFO. Presence of the canted antiferromagnetism of bare HFO at room-temperature with antiferromagnetic transition at ∼ 637 K was confirmed in susceptibility vs. temperature variation and by the nature of MH loops. Interestingly, substantial enhancement of magnetism was observed in HCFTO compared to that of bare one, where the room-temperature maximum magnetization is enhanced by 73%. Dielectric strength of HFO (∼48) is also enhanced highly (∼3.4 times) in HCFTO (∼165), and the loss factor is lowered to nearly half. Current density vs. electric field (J-E) curve suggests the presence of polarization at room temperature with negligible leakage loss. Lower leakage loss of HCFTO indicates better multiferroicity than HFO. Direct measurement of ferroelectric loop shows the room-temperature ferroelectricity of bare HFO (P max ∼ 0.0041 µc/cm2) well improved (∼1.5 times) in the doped HCFTO (P max ∼ 0.0061 µc/cm2) with lower hysteresis loss. Room-temperature magnetoelectric coupling measurements, shows a high value (∼2.47%) of magnetocapacitance in the doped system, which is much higher (∼4.94 times) than the bare one (∼0.5%). All these properties of the sample clearly confirm the co-doping in the HoFeO 3 nanoparticle system results in a considerable improvement in its magnetoelectric behavior, and this co-doped Ho 0.95 Co 0.05 Fe 0.95 Ti 0.05 O 3 system can be a promising and potential magnetoelectric multiferroic for device applications. [ABSTRACT FROM AUTHOR]

The effect of sintering temperatures on the lattice parameters, microstructure and electrical properties of BaTi 0.4 (Fe 0.5 Nb 0.5 ) 0.6 O 3 perovskite ceramics were investigated. Impedance spectroscopy analysis confirms that this material is electrically heterogeneous which plays a major role for the high dielectric constant. The sintering temperatures have a sensitive influence on the values of the dielectric constant. High dielectric constant (12,708) with low dielectric loss (0.23) was achieved at room temperature for 1250 °C sintered ceramic. Activation energy was found to be 0.25 eV and 0.31 eV corresponding to grain and grain boundary, respectively which confirms that the grain boundaries are more insulating than grains. We observed the high magnetocapacitance (5.8%) at 9 kOe for 1250 °C sintered sample which is useful for the practical application. This study will help to modify the BaFe 0.5 Nb 0.5 O 3 based materials and lead to more applications in the microelectronics devices. [ABSTRACT FROM AUTHOR]

We have synthesized NiFe2O4 (φ∼ 6 nm) and Fe3O4 (φ∼ 30 nm) magnetic nanoparticles by solvothermal synthesis; furthermore the Fe3O4 nanoparticles have been coated with a SiO2 shell of approximately 5 nm of thickness by the Stöber method. In the study of the dielectric properties as a function of the frequency, temperature and applied magnetic field, we observe a magnetocapacitive behavior (MC) at room temperature and under a moderate magnetic field (H=0.5T), that is specially important in the case of the Fe3O4, nanoparticles (MC≈ 6%). On the other hand, the NiFe2O4 and Fe3O4@SiO2 samples present smaller magnetocapacitive effects: MC≈ 2% y MC≈ 1%, respectively. These MC values, that are higher than those reported in the literature for other related magnetic nanoparticles, corroborate the theoretical model proposed by Catalán in which the combination of Maxwell-Wagner effects and magnetoresistance promote the appearance of stronger magnetocapacitive effects.Hemos preparado nanopartículas magnéticas de NiFe2O4 (φ∼ 6 nm) y Fe3O4 (φ∼ 30 nm) mediante el método de síntesis solvotermal; además estas últimas han sido recubiertas con una capa de SiO2 de unos 5 nm de espesor mediante el método de Stöber. Al estudiar el comportamiento dieléctrico en función de la frecuencia, temperatura y campo magnético aplicado, observamos un comportamiento magnetocapacitivo (MC) a temperatura ambiente y bajo un campo magnético moderado (H= 0.5 T) que es especialmente importante en el caso de las nanopartículas de Fe3O4 (MC≈ 6%). Por su parte las muestras de NiFe2O4 y Fe3O4@SiO2 presentan efectos magnetocapacitivos menores: MC≈ 2% y MC≈ 1%, respectivamente. Estos valores de MC, que son considerablemente superiores a los descritos hasta el momento para otras nanopartículas magnéticas, corroboran la predicción teórica de Catalán de que la combinación de efecto Maxwell-Wagner con efectos magnetorresitivos potencian la aparición de fenómenos magnetocapacitivos.

In this paper, the magnetocapacitance effect of magnetic particles Fe 3 O 4 embedded in polymer insulating matrix polydimethylsiloxane is investigated using finite element method by commercial software Comsol Multiphysics. With this method, the process of the capacitance variation under different magnetic field is simulated, and the factors influencing magnetocapacitance effect are studied. In particular, we apply the micro-macro coupling method for simulation analysis due to a large amount of calculation in the actual model. First, a three-dimensional microscopic model is calculated to obtain the effect of the magnetic field on the equivalent permittivity of the composite. The relationship is then substituted into the material property of the macroscopic model to simulate the magnetocapacitance effect. The results show that the composite exhibits magnetocapacitance characteristics that are related to the magnetic field intensity, particle size, and particle concentration. The capacitance value increases with the magnetic field at certain particle size and particle volume fraction. Meanwhile, the capacitance value at the same magnetic field increases with the particle size and particle volume fraction. The numerical results are consistent with the experimental results. The simulation model can provide a reference for research on the magnetocapacitance effect involving similar composite systems composed of magnetic particles and polymer matrix. [ABSTRACT FROM AUTHOR]

Multiferroic materials with such magnetoelectric properties that are comparable to the useful ferroelectrics and ferromagnets are exceedingly rare. We report here on integration of ferroelectricity and ferromagnetism in a M-hexaferrite (La 0.2 Pb 0.7 Fe 12 O 19 ), which simultaneously exhibits colossal magnetocapacitance effect at room temperature. The coexistence of the off-centered FeO 6 octahedron and electron spins in partially filled Fe 3d or La 3f orbits is supposed to be responsible for mergence of mutually exclusive electric and magnetic orders. Five magnetoelectric phases and boundaries have been built up by the permeability profile. By applying a magnetic field (B), the capacity or dielectric constant demonstrates giant oscillations, whose maximum amplitude exceeds 1.90 × 10 5 % at 80 Hz. The huge oscillations are associated with the variable component and orientation of the cycloid conic spins at the boundaries between two neighboring magnetic phases, where the cycloid cone axes align themselves parallel or reversal parallel to the direction of B field. Thus the dielectric constants are systematically enhanced to reach a giant value of ε m ± ′ = +58270 or −84866 due to the great promotion of spin-current induced polarization. [ABSTRACT FROM AUTHOR]

We report on the increase in the spin reorientation temperature in HoFe 0.5 Cr 0.5 O 3 compound by isovalent substitution (Cr 3+ ) at the Fe-site and the magnetocapacitance in the HoFeO 3 compound. Spin reorientation transition is evident around 50 K and 150 K for the x =0 and x =0.5 compounds respectively. The increase in the spin reorientation transition temperature in case of x =0.5 compound can be attributed to the domination of the Ho 3+ –Fe 3+ interaction over the Fe 3+ –Fe 3+ interaction. Decrease in Néel temperature from 643 K ( x =0) to 273 K ( x =0.5) can be ascribed to the decrease in the interaction between antiferromagnetically aligned Fe 3+ moments as a result of the dilution of the Fe 3+ moments with the Cr 3+ addition. From the magnetization M vs. magnetic field H variation it is evident that the coercivity, H C decreases for x =0.5 compound, hinting the magnetic softening of the HoFeO 3 compound. Observed magnetocapacitance could be due to lossy dielectric mechanism in the present compound. Indeed, present results would be helpful in understanding the physics behind rare-earth orthoferrites. [ABSTRACT FROM AUTHOR]

Lead-free magnetoelectric (ME) composites with remarkable ME coupling are required for the realization of eco-friendly multifunctional devices. This work demonstrates the ME properties of Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 –CoFe 2 O 4 (BCZT–CFO) core–shell composites synthesized via co-sol–gel technique. Room temperature ferroelectric and ferromagnetic characterization have shown that the samples are magnetic and ferroelectric along with an adequate magnetoelectric coupling of 12.15 mV/(cm Oe). The strong dependence of electric parameters on applied magnetic DC bias fields demonstrated in ferroelectric and magnetoelectric measurements provide a framework for the development of potential magnetoelectric devices. Also, the high sensitivity of magnetoelectric coupling towards the applied AC magnetic field can be used for its application in magnetoelectric sensors. [ABSTRACT FROM AUTHOR]

The properties of (1- x)Ba(FeTa)O- xBiFeO [(1- x)BFT- xBFO] ( x = 0.0, 0.1, 0.3, 0.5) ceramics have been investigated. (1- x)BFT- xBFO powders were synthesized by a modified two-step calcination technique, and ceramics were fabricated by a conventional technique. X-ray diffraction (XRD) analysis revealed that the modified ceramics exhibited a mixture of BFT cubic phase and BFO rhombohedral phase. The peaks shift increased with increasing BFO content to a maximum value for the composition with x = 0.5. The overall shift of the XRD patterns indicated distortion of the unit cell, which may be due to ions from BFO entering the BFT lattice. BFO additive promoted grain growth, while the maximum density of the studied ceramics was observed for the x = 0.1 composition. The modified ceramics presented enhanced thermal and frequency stability of the dielectric constant. BFO additive also reduced the loss tangent for the system. Improvement of the magnetic behavior was observed after adding BFO. Furthermore, all the ceramics, including pure BFT (a nonmagnetic phase at room temperature), presented a magnetocapacitance effect, which can be related to magnetoresistance along with Maxwell-Wagner polarization effects. [ABSTRACT FROM AUTHOR]

Layered composite electro-ceramics can be designed to exhibit the magnetoelectric (ME) effect based on stress transfer from magnetostriction of ferromagnetic layer to the ferroelectric layer. Many studies in search of giant ME coefficients in layered composites have been made but there are less studies regarding the ME effect in these ceramic materials as a function of temperature, mainly at low temperatures. With the influential increase in magnetoelectric sensing devices use in extreme, minute or precise field monitoring, a broadband temperature dependent analysis on ME effect of these sensors is much required. In this work the effect of temperature on ME effect in a NiFe2O4/Pb(Zr0.52Ti0.48)O3/NiFe2O4layered composite are studied and any major/minute change have been analyzed. Dynamic ME measurements shows a maximum linear ME coefficient (αME= 238 mV/cm.Oe) by applying an AC magnetic field in a frequency of 600 Hz at room. Highly reduced αMEvalues are observed at low temperatures. Magnetocapacitance effect studies showed a strong magnetoelectric coupling at room temperature and, also, a dramatic reduction in the magnetoelectric coupling at 200 K and 100 K. Analyzing the phenomena mathematically shows that there is a secondary effect interaction which influences the ME effect intensity depending on temperature. [ABSTRACT FROM AUTHOR]

Hollow-spherical composites of polyaniline/cobalt sulfide/carbon nanodots (PANI/CoS/CDs-0.5T) have been synthesized by in situ polymerization under an applied magnetic field (MF) of 0.5 T. As a control, PANI/CoS/CDs-0T composites have been synthesized without a MF. Both composites acting as electrodes present obvious magnetocapacitances at a scan rate of 100 mV s −1 while the electrochemical cell tested under an external MF of 0.5 T. Notably, PANI/CoS/CDs-0.5T composites show larger magnetocapacitances than PANI/CoS/CDs-0T composites at different scan rates from 5 to 100 mV s −1 . Electrochemical impedance spectroscopy (EIS) results indicate that MF can reduce charge transfer resistance at electrode/electrolyte interface. More importantly, PANI/CoS/CDs-0.5T composites show a much stronger electromagnetic wave (EMW) absorbing capability than PANI/CoS/CDs-0T in the range of 2–18 GHz which is attributed to an increased dielectric loss and a magnetic loss in low frequency range of 2–12.5 GHz. MF-induced ferromagnetic nanodomains of Co 2+ clusters in the PANI/CoS/CDs-0.5T composites increase the complex permittivity and create more interfacial polarizations or the Maxwell–Wagner effect, which leads to increased dielectric loss. Compared with PANI/CoS/CDs-0T composites with diamagnetic behaviour, MF-induced weak ferromagnetism of CoS in the PANI/CoS/CDs-0.5T composites has caused additional magnetic loss. This work provides an efficient way for modulating electrochemical or electromagnetic properties of inorganic/polymer nanocomposites by employing an external MF. [ABSTRACT FROM AUTHOR]

Magnetocapacitance and magnetization behavior as a function of reduction heat treatment at 650 °C and 900 °C in a 5%H 2 –Ar atmosphere on LiNbO 3 nanocrystalline are reported. There is a change of intrinsic dielectric constant ( κ ) from 822 to 860 produced by spin polarization using an external magnetic field. The Raman, X-ray photoelectron spectroscopy and electron paramagnetic resonance spectroscopy, indicate vibration mode changes localized at Nb–O bonds in the octahedron NbO 6 , shifts in the binding energy of the electronic structure of ions of niobium (3 d ) and the oxygen (1 s ). It is due to the oxygen vacancies caused by reduction heat treatment process. Moreover there is ions redistribution of Nb +3 , Nb +4 and Nb +5 at the surface of the nanoparticles. [ABSTRACT FROM AUTHOR]