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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]

[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]

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.

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]

[Display omitted] • CoFe 2 O 4 is embedded in the BaTiO 3 matrix due to adopted ex-situ synthesis. • Interaction of ferrite to ferrite has increased at 1000 °C. • Frequency and field-dependent MC responses are analogous to MR. • Low resistance was observed at 1000 °C from Cole-Cole plots. • Combined effect of M−W polarization and MR lead to maximum MC at 1000 °C. Enhanced magnetodielectric properties including magnetocapacitance have been observed in the BaTiO 3 -CoFe 2 O 4 composites due to the microstructural interactions between the dielectric and magnetic phases. Based on this concept, this research work explores the frequency and field dependent magnetocapacitance and magnetoresistance of 70 wt% BaTiO 3 – 30 wt% CoFe 2 O 4 composites. Ex-situ synthesis method is adopted to form a partial 0–3 microstructure and this composite is sintered at 900 °C and 1000 °C. Phases such as pseudo-cubic BaTiO 3 and cubic CoFe 2 O 4 have been observed in both composites. Secondary phase of barium hexaferrite is observed at 1000 °C. Based on FESEM, CoFe 2 O 4 phase is found to be embedded in the BaTiO 3 matrix at 900 °C, however interconnected CoFe 2 O 4 along with partially shrunk BaTiO 3 has been observed at 1000 °C. The permittivity of composite is found to be ∼ 317 and ∼ 451 at 900 °C and 1000 °C, respectively, and the Maxwell-Wagner polarization is tuned by the microstructure. The effect of space charge is found to be relatively larger at 1000 °C. Magnetic nature is altered due to the connectivity of ferrite phases. Magnetocapacitance values are mostly analogues to the magnetoresistance behavior in both composites. The percentage of magnetocapacitance is found to be increased nearly 5 times due to the microstructural variations. Field and frequency-dependent magnetocapacitance responses along with Cole-Cole plots of composite confirmed the role of microstructural interactions and magnetoresistance. [ABSTRACT FROM AUTHOR]

• Composites of (YAFO) x (BNBT) (1-x) for x = 0.3, 0.5 were successfully synthesized by sol-gel method in pure phase. • Thorough analysis of magnetic properties in temperature range 50–950 K reveals its magnetic nature completely. • High dielectric constant with negligible loss and good ferroelectric ordering was observed. • The sample showed good magnetoelectric coupling having nonlinear variation of magnetocapacitance with a maximum value of 6%. • Nanocomposite of (YAFO) x (BNBT) (1-x) for x = 0.3 system may serve as a potential candidate for multiferroic applications. To derive a new multiferroic nanocomposite, Al-doped YFeO 3 and Ba doped Bi 0.5 Na 0.5 TiO 3 were considered as individual components. (Bi 0.5 Na 0.5) 0.94 Ba 0.06 TiO 3 was synthesized through sol-gel technique and successfully incorporated during the preparation of Y 0.97 Al 0.03 FeO 3 , where two different stoichiometric ratios (YAFO) 0.3 (BNBT) 0.7 and (YAFO) 0.5 (BNBT) 0.5 were considered. Rietveld refinement of X-ray diffractograms confirmed the desired phase formation without any impurity. Different useful structural parameters were evaluated from Rietveld analysis, which is helpful to explore the magnetoelectric behavior of both composites. FESEM micrographs showed spherical/ellipsoidal particles scattered uniformly obeying Gaussian distribution with an average grain size obtained as ∼45.3 nm for (YAFO) 0.3 (BNBT) 0.7 and ∼47.2 for (YAFO) 0.5 (BNBT) 0.5. EDAX spectra confirmed the absence of impurity elements and uniform distribution of constituent elements was confirmed by EDAX mapping. Thermal variation of magnetic susceptibility from 50 K to 950 K was analyzed to know the presence of different magnetic phases in composites. Analyses of zero field cooled and field cooled magnetization variation, observed as a function of temperature and magnetization vs field loops, recorded by VSM reveal the presence of antiferromagnetism in both composites with a maximum magnetization of 0.85 emu/g for (YAFO) 0.3 (BNBT) 0.7 and 1.12 emu/g for (YAFO) 0.5 (BNBT) 0.5 at room temperature (300 K). Dielectric properties observed as a function of temperature (300–450 K) and frequency (100 Hz to 5 MHz) provided various important information like permittivity, loss factor, ferroelectric to paraelectric transition temperature, etc. Room temperature dielectric strength of ∼240 with a very low loss of ∼5, indicates good dielectric nature of both composites. Direct observation of the ferroelectric loop indicates the presence of better ferroelectricity in (YAFO) 0.3 (BNBT) 0.7 (P max – ∼0.029 µc/cm2) compared to (YAFO) 0.5 (BNBT) 0.5 (P max – ∼0.018 µc/cm2). Magnetocapacitance coefficient is also higher in (YAFO) 0.3 (BNBT) 0.7 (∼6%) compared to (YAFO) 0.5 (BNBT) 0.5 (∼4%). All these investigations suggest that (YAFO) 0.3 (BNBT) 0.7 can be considered a potential candidate as type II magnetoelectric multiferroic. [ABSTRACT FROM AUTHOR]

Without changing the crystalline structure of BaFe 10.2 Sc 1.8 O 19 (BFSO) epitaxial thin film, significant modulation of its saturation magnetization (from 75 to 180 emu/cc), magnetic anisotropy field (from 3590 to 1434 Oe) and multiferroic ordering temperature (from 207 to 306 K) can be realized with different densities of lattice defects (DLD). A defects-related effective magnetic field H eff is defined. H eff reduces obviously with increasing annealing temperature T A , agreeing well with the reduced DLD. The defects-related magnetic ordering of BFSO films is further verified in the magnetocapacitance devices. The magnetocapacitance for 1000 °C annealed film is more than 5 times larger than that of as-deposited film. This can be explained by the ultra-sensitive of non-collinear conical magnetic structure and spin-phonon coupling in BFSO to the DLD related local lattice structure. The above findings enable better understanding and usage of lattice defects on regulating the physical properties of multiferroic hexaferrite devices. [Display omitted] [ABSTRACT FROM AUTHOR]