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Spintronic devices that utilize spin transfer torque are promising for integrated memory applications. However, these devices face substantial energy consumption challenges due to the high current densities required for switching. Conversely, voltage‐driven spintronic devices, using capacitive displacement charge, can realize switching operations that are energy‐efficient (≈1–10 fJ bit−1). This work investigates switching based on voltage control of the interlayer exchange coupling in perpendicular magnetic anisotropy (PMA) multilayered heterostructures. Unlike previous works that utilized gating techniques that employ ionic transport mechanisms to control interlayer exchange coupling, this study employs electrostatic gating by using MgO, which is more compatible with modern spintronic‐based memories. These results suggest that the magnetization anisotropy, and the magnitude, and phase of the Ruderman‐Kittel‐Kasuya‐Yosida (RKKY) coupling function with spacer layer thickness can be controlled through electric gating, providing a promising avenue for the development of energy‐efficient magnetic data storage devices. [ABSTRACT FROM AUTHOR]

We report the preparation and characterization of vanadium substituted four-layer Aurivillius compound Bi5Fe1.5V0.5Ti2O15 using spin coating method. Ferroelectricity in the prepared films are confirmed from the well saturated polarization vs electric field (P-E) loops having remnant polarization (2 Pr) around 12.94 µC/cm2 at room temperature. In addition, low temperature P-E measurements show a decrease in Pmax and 2 Pr, which is attributed to the stabilization of defect dipole complexes and domain pinning, as seen in bismuth-based ferroelectrics. Additionally, this decrease in polarization is accompanied by an increase in imprint, confirming the presence of defect dipoles manifested as internal fields. [ABSTRACT FROM AUTHOR]

The present work deals with the calculation of electrocaloric (EC) coefficients of BaTi1-xSnxO3 (x = 0.15, 0.20, 0.30) polycrystalline ceramics. Dielectric and polarization studies are carried out in a temperature range of 100 − 300 K to calculate the EC coefficients employing the indirect method based on Maxwell's equations. It is demonstrated that the EC effect is enhanced near the dielectric maxima for all the samples, including that of samples which exhibit relaxor behavior (x = 0.30). Furthermore, the maximum change in temperature, the temperature at which the maximum EC coefficient is achieved and the working range for EC effect are shown to be tunable with electric field and Sn substitution. [ABSTRACT FROM AUTHOR]

The present work reports the structural, electrical and magnetic properties of W6+ and Mo6+ substituted four-layer Aurivillius compound, Bi5FeTi3O15 (BFTO). The oxidation states of the dopants and other elements of BFTO are studied from x-ray photo-electron and 57Fe Mössbauer spectroscopy. The substitution resulted in a net increase of magnetic cation (Fe3+) from 25% to about 37.5% in BFTO. However, the magnetization measurements indicate the lack of magnetic ordering even down to 2 K. Further, the high temperature (300-1070 K) dielectric study of these compounds reveal the ferroelectric transition temperature decreases with the increase of magnetic cations in BFTO because of hexavalent W6+ and Mo6+ substitution at Ti4+ site. [ABSTRACT FROM AUTHOR]

Here, we report detailed studies on magnetic phase transitions and magneto-electric (ME) coupling in Fe 1 - x Ce x VO 4 . X-ray diffraction (XRD) and Raman spectroscopic measurements confirm triclinic crystal structure (P-1) with small variation in lattice parameters and Ce incorporation into the FeVO 4 lattice up to 10% of Ce. The presence of local lattice distortions and electronic inductive effect in FeVO 4 between Fe 3 + and V 5 + ions were found in X-ray absorption near edge structure (XANES) studies due to the presence of Fe 3 + –O– V 5 + linkages. Two antiferromagnetic (AFM) transitions similar to FeVO 4 appear at 21.86 K and 16.03 K, and Ce doping has little effect on the magnetic transitions. 57 Fe Mössbauer spectroscopic results show the invariance of Fe valance. Low temperature high magnetic field Mössbauer data depicts the presence of spiral AFM order in all the samples. A sharp peak at 16.0 K in dielectric permittivity with minimal suppression due to applied magnetic field is observed indicating the presence of ferroelectricity and magneto-dielectric coupling. Magnetic and ME transitions are almost robust against Ce doping. [ABSTRACT FROM AUTHOR]

This study demonstrates the magneto‐dielectric (MD) properties of high quality epitaxially strain multiferroic SrMnO3 thin film on conducting Nb doped SrTiO3 substrate. The study observes considerable high positive MD coupling near room temperature and across the anti‐ferromagnetic transition temperature of SrMnO3. The dielectric maxima of the grown film is above room temperature, which confirms the room temperature ferroelectric nature of the grown film. From out‐of‐plan polarization and PUND (Positive Up Negative Down) measurements in the presence of magnetic field, it is confirmed that the polarization value of grown SrMnO3 thin film increases with an increase in magnetic field. In this study, the oxygen off‐stoichiometry concentration is also varied by varying oxygen partial pressure during deposition and is able to create Mn4+, Mn3+, and Mn2+ in the grown films. Despite having mixed Mn states, SrMnO3 thin films remain in the insulating phase. So, the insulating nature of SrMnO3 thin film is robust with respect to oxygen off‐stoichiometry and vacancy/substrate induced strain mediated change in the crystal field. The study has also demonstrated the variation of MD in SrMnO3 thin film by change in oxygen vacancy induced modification in crystal field. [ABSTRACT FROM AUTHOR]

Here we report the evidence of an additional magnetic ordering and frequency dispersive magneto-dielectric (MD) permittivity besides multiferroic behavior in Te 4+ ( S = 0) doped FeVO 4 . Two antiferromagnetic transitions similar to FeVO 4 at ∼21.86 K (TN1) and 16.03 K (TN2) were observed in all samples. An additional novel defect clusters based magnetic ordering at relatively higher temperature (TAMO) ∼ 203 K is also observed from the magnetization. Evaluated magnetic moments show systematic decrease and the magnetic frustration factors show an increase with the increasing of Te 4+ ( S = 0) content. MD studies show stable ferroelectric ordering at spiral magnetic transition (TN2) and the multiferroic order persists to the largest doping of Te ( x = 0.10). The MD studies also reveal a magneto-capacitive (MC) behavior at TAMO(∼203 K) with a high dielectric constant and loss, and the possible reason for the magnetic ordering and MC behavior is ascribed to short range magnetic clustering arising out of defect based mechanisms. Mössbauer spectroscopic studies confirm local structural correlation with magnetic and ferroelectric ordering., (© 2023 IOP Publishing Ltd.)

The present work reports polarization response and the effects of ac - & dc -fields on 30% Sn doped BaTiO 3 polycrystalline relaxor thin films as a function of temperature. Apart from the low temperature frequency dispersion in dielectric data, a frequency independent local maxima in dielectric constant and a concomitant peak in dielectric loss at T * ∼ 245 K is observed, which is unusual of bulk relaxor systems. Below T *, dispersion in dielectric constant becomes quite evident showing signatures of non-ergodic behavior. Subsequently, the dielectric and polarization responses in ergodic (> T *) and non-ergodic (< T *) states are studied to determine the polar state in the system. The ac -field dependence of permittivity indicates the presence of domain like dynamics, predominantly in non-ergodic state. Field induced transition to ferroelectric state, both in ergodic and non-ergodic phases, is demonstrated from the dc -field studies. Further, the dc -field and polarization hysteresis studies reveal the system resembles that of anti-ferroelectric systems below T *, a possible signature for the existence of incommensurate polar regions. These experimental results put together, provides key insights in understanding the field effects of relaxor behavior in doped barium titanate systems., (© 2021 IOP Publishing Ltd.)

We have investigated magnetic, structural and dielectric properties of Bi 5 FeTi 3 O 15 (BFTO) in the temperature range 5K-300 K. Using diffraction, Raman spectroscopy and x-ray absorption fine structure measurements, iso-structural modifications are observed at low temperatures (≈100 K). The analysis of dielectric constant data revealed signatures of dielectric relaxation, concomitant with these structural modifications in BFTO at the same temperatures. Further, employing complementary experimental methods, it is shown that the distribution of Fe/Ti ions in BFTO is random. With the help of techniques that probe magnetism at various length and time scales, it is shown that the phase-pure BFTO is non-magnetic down to the lowest temperatures., (© 2021 IOP Publishing Ltd.)