Lossy Behavior Research Articles

Gd3+ doped CoCr2O4 nanoparticles: tuning the physical properties and optimizing the hyperthermia efficacy.

Tuning the physical properties of nanomaterials is essential to enhance their capabilities for modern technological applications. Incorporating appropriate dopant ions is expected to modify the physical properties of nanomaterials significantly. In this study, the microstructural, magnetic, electronic and optical properties of cobalt chromite nanoparticles have been tuned by incorporating Gd ions to obtain the optimized conditions for self-heating efficiency. Four chromite samples with varying Gd3+ dopant concentrations [CoGd x Cr2-x O4: x = 0, 0.04, 0.08 and 0.12] were prepared using the standard chemical co-precipitation method and their physical properties were explored thoroughly. The Gd3+ dopants in the host CoCr2O4 structure were shown to be capable of regulating the physical properties of the doped nanomaterials. Formation of a pure cubic spinel crystallographic phase together with size, shape and developed microstrain in the synthesized doped chromites were analyzed precisely and it was found that the mean size decreased gradually as the Gd content increased. Higher Gd content chromite nanoparticles showed a distinct blue shift in their absorption spectra and an increase in specific surface area, as evidenced by the BET study confirming the reduction in mean diameter. Substituted Gd ions also tuned the dielectric characteristics of the host chromite nanomaterial. A careful investigation of electrical conductivity in varying electric fields indicated that electron hopping occurs mostly during charge conduction. All the chromite samples exhibited lossy dielectric behavior as the dopant fraction increased. Introducing Gd ions in nanocrystalline cobalt chromite diluted the magnetic properties, which was evident from the reduction of the coercive field, and also provided the superparamagnetic ground state above 95 K. The spin-spiral transition became visible near 26 K as the Gd content in pure CoCr2O4 nanoparticles increased. The induction heating properties of nanosized chromite samples were modified using Gd doping, and the impacts of both the anisotropic energy barrier and magnetic dipole-dipole interactions on hyperthermia efficacy were extensively investigated. All of the prepared chromite samples at low concentration (1 mg mL-1) attained temperatures between 34.7 °C and 35.7 °C from ambient temperature in 900 seconds with an observed drop in the induction heating temperature with increasing Gd content in nanosized cobalt chromites. It was observed that the dispersion level of nanoparticles in solution also determined the heating efficiency. It was observed that Gd doped CoCr2O4 nanoparticles have the potential to be used in magnetic hyperthermia applications.

Crystallographic Profiling, Core-Shell Electronic Configurations, and Investigations of Frequency-Dependent Dielectric Characteristics of Sb2O3-V2O5 Micro Ceramics

A series of V2-xSb2xO5-δ (Sb-V-O) ceramic powder samples with molar concentrations ranging from 0.05 to 0.08 were synthesized using a solid-state reaction method. Crystallographic analysis conducted through Rietveld refinement indicates that at a molar fraction of x=0.05, the orthorhombic V₂O₅ phase is observed. Conversely, at molar concentrations of x=0.06, 0.07, and 0.08, the orthorhombic phase of V2O5 and the tetragonal phase of SbVO4 are present simultaneously. X-ray photoelectron spectroscopy (XPS) was employed to ascertain the elemental oxidation states, revealing the presence of V5+, V4+, Sb3+ ions, and Sb0 metal atoms, along with O1s photoelectron peaks. The photoluminescence (PL) emission spectrum suggests transitions from a shallow donor level to the valance band. The room temperature AC conductivity and dielectric property results reveal a systematic decrease in the dielectric constant. The AC conductivity experimental data was accurately modeled using the Almond-West formalism, yielding high R2 values (0.9968–0.9986) and low chi-square errors (1.157×10⁻11–9.42×10⁻12) obtaining hopping frequency values for each composition (x = 0.05–0.08). AC conductivity (σac) decreased from 5.08×10⁻⁴ S/m to 2.40×10⁻⁴ S/m at 10 MHz, while DC conductivity (σdc) dropped from 7.22×10⁻⁵ S/m to 1.55×10⁻⁵ S/m. This reduction in conductivity is attributed to structural changes from Sb³⁺ substitution, which disrupts polaronic conduction by reducing the number of available O2⁻ ions and promoting SbVO₄ phase formation, hindering charge transport. The Sb₂O₃-V₂O₅ ceramics exhibit promising potential for energy storage applications, particularly in capacitors requiring high dielectric constants at low frequencies. At lower frequencies, grain boundaries inhibit conduction, enhancing dielectric constant values; at elevated frequencies, grain conduction predominates, lowering dielectric constant in accordance with Koop’s phenomenological theory, favoring applications in multi-layer ceramic capacitors. A notably higher dielectric loss factor (εr'') at low frequencies (10 Hz–1 kHz) indicates lossy behavior, beneficial for microwave absorption, while its stabilization above 10 kHz suggests minimal energy dissipation, ideal for high-frequency electronic and dielectric devices.

Synergetic effect of hexaferrite and reduced graphene oxide (rGO) in photothermal therapy and hyperthermia applications

This research article describes the synthesis of composite materials by combining T-type hexagonal ferrite and reduced Graphene Oxide using the standard ceramic process. The Calcium-based T-type hexagonal ferrite was synthesized by using the sol-gel auto-combustion method while the reduced graphene oxide by adopting the Hummer method. The crystallite size varied in the range of 23.38 -39.16 nm as calculated from the X-ray diffraction (XRD) data. Consequently, the lattice parameters 'a' and 'c' decreased from 5.9 to 5.1 Å and from 29.92 to 28.32 Å, respectively. The use of atomic force microscopy (AFM) revealed a range of particle sizes at the surface, varying from 1.70 nm to 3.85 nm. Moreover, the saturation and remanence magnetization values demonstrated an increasing trend with T-type hexaferrites concentration whereas the coercivity decreased. The UV–vis near-infrared spectra exhibited substantial light absorption, characterized by a wide absorption range in the visible and near-infrared (NIR) region (700–1100 nm) which indicates its use in Photothermal therapy (PTT). The Calcium T- type hexaferrite exhibited clear peaks in the blue, green, violet, and yellow spectra in its photoluminescence (PL) properties. These peaks are believed to be caused by oxygen vacancies and defects. The synthesized samples displayed a lossy behavior in the polarization-electric field (P-E) loop, with saturation polarization levels exceeding remnant polarization, which is an amenable condition for lossy behavior. Most importantly, the synthesized materials had significant thermal responses when exposed to an alternation (AC) magnetic field, indicating their potential use in magnetic hyperthermia applications.

Influence of Mg2+ substitution on structural, electrical polarization, and magnetic properties of Sr-based R-type hexagonal ferrites

Substitutional effects of Mg2⁺ proceeding the structural, Fourier-transform infrared spectroscopy, scanning electron microscopy, and vibrating sample magnetometer characteristics of Sr₁₋ₓMgₓMn₂Fe₄O₁₁ R-type hexaferrite were systematically investigated for different concentrations (x = 0, 0.25, 0.75, 1.0). Sol-gel technique was adopted to fabricate the material. X-ray diffraction analysis confirmed samples exhibit a single-phase structure of MgMn₂Fe₄O₁₁. Lattice parameters (a and c) and V (unit cell volume) decreased with increasing Mg concentration. Also, a rise in dislocation density was observed, while crystallite size varied. FTIR spectra further corroborated the single-phase hexagonal structure of the manufactured samples. The electric polarization (P-E) loops demonstrated that saturation and Pr remanent polarization increased with Mg substitution, while lossy behavior decreased. Magnetic measurements revealed that substituting Mg2⁺ directed toward an initial escalation in saturation magnetization, retentivity, and coercivity, followed by a subsequent decline. Furthermore, VSM analysis indicated that all samples exhibited a combination of ferrimagnetic and paramagnetic behavior.

Stable and low loss oxide layer on α-Ta (110) film for superconducting qubits

The presence of amorphous oxide layers can significantly affect the coherent time of superconducting qubits due to their high dielectric loss. Typically, the surface oxides of superconductor films exhibit lossy and unstable behavior when exposed to air. To increase the coherence time, it is essential for qubits to have stable and low dielectric loss oxides, either as barrier or passivation layers. In this study, we highlight the robust and stable nature of an amorphous tantalum oxide layer formed on α-Ta (110) film by employing chemical and structural analyses. Such kind of oxide layer forms in a self-limiting process on the surface of α-Ta (110) film in piranha solution, yielding stable thickness and steady chemical composition. Quarter-wavelength coplanar waveguide resonators are made to study the loss of this oxide. One resonator has a Qi of 3.0 × 106 in the single photon region. The Qi of most devices are higher than 2.0 × 106. Moreover, most of them are still over 1 × 106 even after exposed to air for months. Based on these findings, we propose an all-tantalum superconducting qubit utilizing such oxide as passivation layers, which possess low dielectric loss and improved stability.

Investigation of BaTiO3/ Cu1-xMgxFe2O4 nano-multiferroic composites

In the present work, the citrate precursor approach has been used to generate nano-particle ferrites with the chemical composition Cu1-xMgxFe2O4 (where x = 0.0, 0.5, and 1). Multiferroic composites of BaTiO3 along with the three samples of Cu-Mg ferrites have been prepared using two percentages of BaTiO3 (30 % and 70 %) with each one of the three ferrites. X-ray fluorescence (XRF) and X-ray diffraction (XRD) have been used to characterize the samples under investigation, indicating that the intended samples have formed without impurities. The average particle size of the samples has been estimated from the XRD patterns (64.1 nm for BaTiO3, 85.8 nm for CuFe2O4, 83.5 nm for Cu0.5Mg0.5Fe2O4 and 89.2 nm for MgFe2O4) and have been fairly verified using a transmission electron microscope (TEM) too. A vibrating sample magnetometer (VSM) has been used to study the magnetic characteristics; where the maximum saturation magnetization is recorded for the Mg ferrite as 26.549 emu/g and the maximum coercive field is found for the Cu ferrite as 1085.13G. A variation of the examined samples from hard to soft ferrite has been noticed by introducing Mg such that we can conclude that the Cu0.5Mg0.5Fe2O4 and MgFe2O4 samples may be suitable for high-frequency devices. The decrease in magnetic properties with introducing BaTiO3 has been recorded too. The ferroelectric properties have been investigated and the results show a ferroelectric behavior of BaTiO3 that reveals its nanostructure. An enhancement of conduction current has been recorded by the addition of CuFe2O4, MgFe2O4, and Cu0.5Mg0.5Fe2O4. The maximum values of conduction current have been achieved the pure Mg ferrite and at the samples containing 70 % ferrites in the composite samples in agreement with literature. Finally, it is worth mentioning that the samples exhibiting lossy capacitor behavior may be used as piezoelectric actuators.

Raveling out the effect of Pr3+ ions substitution on different properties of nano-sized hexagonal ferrites

The development of a new stable phase/type, a rare earth element Pr3+ substitution in Ca2-xPrxFe8O14 (T-type) of hexagonal ferrites with composition (x = 0.0, 0.02, 0.06, 0.1), using the sol–gel auto-combustion method was endeavoured in the current study. The x-ray diffraction analysis proved that all samples possess single-phase structures. All computed structural characteristics varied with Pr3+ substitution. The particles with random shapes and sizes were examined from TEM analysis and particle sizes ranged from 14 to 44 nm. With Pr-contents, the saturation and remanent magnetization increased and the coercivity decreased. All samples have high values of dielectric loss, dielectric constant, and tangent loss at low-frequency values and these high values declined with rising frequency. The peaks in real part of the electric modulus migrated toward the low-frequency region; it was the confirmation that grain boundaries are incredibly active to participate in resistance. The uneven trend in the imaginary part of the electric modulus, which is demised with increasing frequency and peaks, was described by the Sillars model. The band gap (Eg) of the samples reduced linearly from 4.60 to 4.32 eV with the addition of Pr3+ ions, as observed from the UV–visible absorbance spectra. The polarization vs electric field (P-E) loops of synthesized samples displayed lossy behavior and this loosy behavior decreased with Pr-additives. On the basis of properties exhibited by the present synthesized T-type hexagonal ferrites, it can be hoped that these materials are applicable in high-frequency devices, antenna, radar applications, and opto-magneto applications.

Influence of Mg2+ Substitution on Structural, Electrical Polarization, Optical Properties and magnetic Properties of Sr-Based R-Type Hexagonal Ferrites

In this research work the substitutional effect of Mg2+ on Structural, Electrical Polarization, FTIR, SEM and magnetic properties of Sr1-xMgx Mn2 Fe4 O11 R-type hexaferrite nanoparticles with compositions (x= 0, 0.25, 0.75,1.0) were investigated. The sol-gel auto-combustion method was adopted to synthesize the samples, and the powder was sintered at 800°C for 4 hours to achieve the stable hexagonal phase. XRD pattern showed that all the prepared samples have a single phase R-type hexagonal structure. The lattice parameter a, c, and unit cell volume V decreased with Mg substitution. The dislocation density increased with Mg substitution, while crystalline size varied with Mg doping. The Fourier transform infrared spectroscopy (FTIR) spectra further verified the single hexagonal phase of the produced samples. The saturation and remanent polarization increased with Mg substitution in the polarization versus electric field loops. The P-E loops also indicate the lossy behavior decreased with Mg substitution. By substituting Mg+2, the saturation magnetization, retentivity, and coercivity increased initially, then decreased. VSM measurements reveal ferrimagnetic and paramagnetic nature for all the samples.

Structural, Morphology, Electrical Polarization and FTIR Properties of Zn Substituted T-type Hexagonal Ferrites

A series of divalent Zn substituted T-type hexagonal ferrite material having the composition (x= 0.0, 0.02, 0.06, 0.1) was synthesized by using the sol-gel auto combustion method. Structural, morphological, optical, and electrical properties of T-type hexagonal ferrite were explored by using an X-ray diffractometer, scanning electron microscopy, Fourier transform infrared spectroscopy and Precision multiferroic II. The X-ray diffraction (XRD) patterns showed the single hexagonal phase ferrites for all the samples. With the substitution of the ions, the change in the values of lattice constants ‘a’, ‘c’ and unit cell volume was observed. The Debye Scherrer formula was used to calculate the crystallite size which was determined to be varied in the range of 26.3nm to 28.3nm. FTIR spectra also indicated that the present synthesized material had single-phase hexagonal structure. SEM micrographs revealed the agglomeration of small grains. The average grain size was found to be 0.331um which might be suitable for microwave absorption applications. The Polarization verse Electric field (P-E) loops unveiled the increase in saturation and remnant polarization. The P-E loops also exhibited the lossy behavior after substitution and the increase in lossy behavior with substitution results in an increase in conductivity of the material.

Unraveling the structural, electrical Polarization, FTIR, Thermal and electrochemical properties of Dy 3+ substituted ?-ferrites

This research article reveals the effect of Dy +3 substitution on ?-ferrites KFe 11-x Dy x O 17 with composition (x=0.00, 0.25, 0.50, 0.75 and 1.0). The samples were synthesized by sol-gel auto- combustion method, sintered at 950 o C temperature. The XRD patterns confirmed the single phase of the synthesized samples. The crystallite size varied in the range of 21.49 nm to 25.24 nm for all samples. The polarization verses electric field (P-E) loops indicated the loosy behavior in all samples. The lossy behavior of the samples was seemed to be increased up to x=0.5 and then decreased. The theoretical expression was used to fit an upper branch of P-E loops. FT-IR spectra showed absorption bands at different wavenumbers due to M-O-M stretching vibrations, H-O-H stretching, and C-O-C stretching vibrations, which also confirmed the formation of the single-phase in the samples. Electrochemical measurements of synthesized nano ferrites were carried out by using cyclic voltammetry in a 3.0 M KOH solution. Electrochemical impedance spectroscopy (EIS) has been described by Nyquist plots.

Architecture inspired structure engineering toward carbon nanotube hybrid for microwave absorption promotion

SummaryConstructing sophisticated 3D structure has been shown to be fruitful in developing carbon nanotubes (CNTs) microwave absorbers (MAs). However, issues with the unclear electromagnetic (EM) responding synergy of CNTs toward substrate and the limited dissipation property caused by the large dense CNTs networks throughout the reported models still need to be resolved. Inspired by the creeper-window-room-structured architecture, an analogous conformal nanostructure of amorphous carbon/CNTs (N-AC/CNTs) hybrid is constructed through an in situ autocatalytic planting approach. By this model, not only the inheritance of frequency dependence characteristic but the co-inheritance of lossy behavior and impedance matching is demonstrated. Moreover, by virtue of the unique structure, a synergistic reinforcing dielectric loss from conductive loss and dielectric polarization was introduced. Therefore, N-AC/CNTs-750 shows impressive EM performance. This work hereby unveils the synergy of EM response from CNTs toward substrate, and provides a pioneering insight into developing architecture-inspired structure engineering to construct high-performance MAs.

Structural and electrical response of poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) copolymer free‐ standing films

AbstractPoly(vinylidene fluoride) (PVDF) based polymers were studied as potential dielectric candidates for polymer film capacitors. The present work focused on the structural and electrical responses of PVDF homopolymer and P(VDF‐CTFE) copolymers (CTFE, chlorotrifluoroethylene). The solvent casting technique was used for the fabrication of free‐standing polymer films. PVDF and P(VDF‐CTFE) copolymer films with different CTFE content were cast under different processing conditions. The structural response of these semicrystalline polymer films showed the existence of crystalline phases and changes in crystallinity depending upon the preparation conditions and CTFE content. The electrical responses of PVDF and P(VDF‐CTFE) copolymers were investigated under the application of low and high electric fields. For the dielectric study, temperature‐dependent dielectric measurements at different frequencies were assessed. Dielectric relaxation in the vicinity of the glass transition temperature was observed along with quantification of activation energies. The effect of CTFE content is also presented. Features such as interface polarization was observed in the high temperature regime. Furthermore, room temperature polarization versus electric field loops of PVDF and P(VDF‐CTFE) copolymers were measured at frequency values of 400 and 10 Hz. All PVDF and P(VDF‐CTFE) copolymers at low frequency showed lossy capacitor behavior which was further investigated by measuring polarization versus electric field loop over a wide range of frequencies, i.e. 0.1–400 Hz. Polarization values of PVDF and P(VDF‐CTFE) copolymer films with different CTFE content were compared on the bases of local dipole moments. © 2022 Society of Industrial Chemistry.

The role of salts selection on phase formation and electrical properties of K0.5Bi0.5TiO3 ceramics fabricated via molten salt synthesis

The present study reveals the effect of salts (NaCl and KCl) on the chemical composition, structural, and electrical properties of intended K0.5Bi0.5TiO3 (KBT) ceramics fabricated via the molten salt synthesis (MSS) route. The average grain size (∼6 μm (±1.1 μm)) and elemental distribution observed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) on KBT ceramics prepared using NaCl as the salt (named KBT-Na) signify the formation of Na0.5Bi0.5TiO3 (NBT) phase instead of KBT ceramic. The Rietveld refinement on X-ray diffraction (XRD) data and temperature-dependent dielectric behaviour of KBT-Na sample further validate the formation of NBT phase. The obtained results suggest the reaction of NaCl salt during the MSS of the KBT-Na sample. Moreover, the structural analyses of KBT ceramic synthesized using KCl salt (named KBT-K) suggested the presence of a minor Aurivillius phase (K0.5Bi4.5Ti4O15) which could be related to undesired reaction kinetics in MSS. The higher room temperature conductivity (∼10−6 Scm−1) and lower piezoelectric coefficient ((d33) ∼ 4–5 pC/N) indicate the loss of stoichiometry in both KBT-Na and KBT-K ceramics during the removal of salts. The observed results in KBT-Na & KBT-K were systematically compared with pure NBT & KBT ceramics prepared using the conventional solid-state synthesis route. The possible reasons for the lossy behavior of MSS synthesized samples are also discussed.

Compositional-driven multiferroic and magnetoelectric properties of NdFeO3-PbTiO3 solid solutions

ABSTRACT Synthesis of polycrystalline (Pb1-x Nd x )(Ti1-x Fe x )O3(for x = 0.21–0.30) solid solutions using solid-state reaction method has been reported. The structural, dielectric, ferroelectric, magnetic, and magnetoelectric properties of the resulting solid solutions have been investigated in detail. The XRD data show that the phase transition occurs at 0.27 ≤ x ≤ 0.28 at room temperature. The dielectric studies show that the transition temperature continuously decreases with increasing “x”. So it is clearly evident from XRD and dielectric data that the tetragonal to cubic phase transition occurs at x = 0.27 to x = 0.28 at room temperature. The remnant polarization (Pr) decreases from 19.78 μC/cm2 to 11.13 µC/cm2 gradually up to x = 0.25 whereas other samples exhibit lossy behavior. The remnant magnetization (Mr) continuously increases from 0.068 emu/g to 0.467 emu/g with composition. All samples exhibit a positive magnetoelectric effect which is the strongest in x = 0.22 sample.

Investigations on multiferroic properties of lead free (1-x)BCZT-xCZFMO based particulate ceramic composites

Present research work describes in detail the investigations related with the multiferroic properties of (1-x)Ba0·85Ca0·15Ti0·9Zr0·1O3-xC0.6Zn0·4Fe1·7Mn0·3O4 [(1-x)BCZT-xCZFMO]; x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1.0 composites, synthesized by conventional solid-state route. X-Ray Diffraction (XRD) patterns have predicted the perovskite tetragonal and spinel cubic structures of BCZT and CZFMO, respectively. Nearly spherical grains of BCZT and CZFMO have been observed through the Scanning Electron Microscopy (SEM) images, whereas non-uniform plate-like morphology has been indicated for the composites. The lossy behavior of composites with the increase in ferrite concentration is evident from the Polarization versus applied electric field (P-E) hysteresis loops. The well-saturated magnetization versus applied magnetic field (M-H) hysteresis loops has been obtained for the composites. In temperature dependent dielectric measurements, ferroelectric to paraelectric phase transition of BCZT is affected by the concentration of the ferrite phase, indicating the presence of magneto-electric coupling effect (ME) in composites. Further, the composites have also shown magnetodielectric (MD) response, which provides a pathway to quantify ME coupling by evaluating various coupling coefficients. The maximum values of MD coefficient, ME coupling coefficient (γ), ME voltage susceptibility (χE) and ME susceptibility (χ) have been found to be −0.72%, 2.372 × 10−4 (g/emu)2, −2.415 mV/cm.Oe and −1.397 × 10−11 s/m, respectively for x = 0.1 composite, which has been found to decrease at higher ferrite concentrations.

Electromagnetic Characterization of Graphene-Plasma Formations

This article presents an efficient electromagnetic (EM) characterization technique to extract the permeability and permittivity tensors of multilayer graphene-plasma formations. This method uses the scattering parameters of normally incident circularly polarized plane waves in free space, making use of the circular polarization to deal with the discontinuity ambiguities in the extracted tensorial permeabilities and permittivities. The proposed method directly determines the linear permeability and permittivity tensors from the combined parameters that are deduced from the circularly polarized wave components. This simple procedure succeeds in overcoming the limitation to usable terahertz and optical frequency bands suffered by existing extraction techniques for lossy and lossless anisotropic material behavior. The retrieved graphene-plasma tensor elements are validated by means of comparison with analytical parameters obtained by solving the original EM problem using the transfer matrix method extended for the circularly polarized fields.

La3+-substituted β-ferrite: Investigation of structural, dielectric, FTIR and electrical polarization properties

Abstract This research article reports the exploration of structural, dielectric, optical and electrical polarization properties of β-type hexagonal ferrite KLaxFe11-xO17 upon the substitution of rare earth element La3+ with compositions (x = 0, 0.02, 0.06 and 0.1). The samples were synthesized by adopting the sol-gel auto-combustion technique and the sintering temperature was 950 °C. The XRD patterns revealed the single hexagonal phase for all the samples. The lattice parameters a (A), c (A), crystallite size (nm), X-ray density (g/cm3) and unit cell volume V (A) 3 changed with La3+ substitution. The crystallite size was found to be varied in the range from 24 to 27 nm for all samples as calculated from Scherer formula. Fourier transform infrared spectroscopy (FTIR) spectra also confirmed the single phase for the synthesized samples. The dielectric constant exhibited the higher values than the pure sample with substitution. The dielectric constant results were fitted with the Debye function which indicated the participation of more than one ion in the increment of dielectric constant. The real (M′) and imaginary (M″) part of complex modulus graphs delineated the peaks shifting towards high and low frequency region which confirmed the occurrence of relaxation phenomenon in material. The polarization verses electric field loops corroborated the decrease in saturation and remnant polarization with La3+ contents. The P-E loops also showed the lossy behavior and the increment in lossy behavior with substitution pointed out the increase in resistivity of the samples. From aforementioned evidences, it is confirmed that the present synthesized beta ferrites are useful in the fabrication of humidity sensors and to reduce the eddy current losses.

Antiferromagnetic and dielectric behavior in polycrystalline GdFe0.5Cr0.5O3 thin film

Single phase materials with both spontaneous electric polarization and magnetization are rare, despite remarkable efforts in developing magnetoelectric multiferroics. In this work, a single-phase polycrystalline GdFe0.5Cr0.5O3 (GFCO) thin film was spin-coated onto a platinized silicon substrate. X-ray diffraction data suggest that the film exhibits an orthorhombic perovskite structure with a Pbnm space group. No other impurity phases were detected. Magnetization measurements reveal the Néel temperature of the GFCO film to be ∼220 K and illustrate a weak ferromagnetic component at 5 K, which could be due to spin canting. Frequency dependent ferroelectric–paraelectric transition was observed around 480 K, indicating the diffuse relaxor-like behavior. The electric field dependent polarization measurements show a lossy behavior below 200 K. The electric field dependent dielectric constant (tunability) measured at 1 MHz in a wide temperature range reveals that the tunability maximizes near the observed dielectric maxima, which further confirms the ferroelectric to paraelectric transition in the present film.

An experimental insight of the multiferroic properties of magnetoelectrically coupled xLNCZFO+(1−x)BSTDO composites

The conventional solid-state reaction method was used to synthesize the xLi0.1Ni0.3Cu0.1Zn0.4Fe2.1O4+(1−x)Ba0.95Sm0.05Ti0.95Dy0.05O3 multiferroic composites. X-ray diffraction patterns confirmed the coexistence of the constituent phases in the composites. Field Emission Scanning Microscopy images showed that the average grain size increased with the ferrite content in composites. The compositional study confirmed that the proportion of the components is well compatible with their nominal compositions. The real part of the initial permeability was found to increase, but the magnetic loss decreased with ferrite content. The dielectric dispersion was observed at lower frequencies on account of interfacial polarization. The maximum dielectric constant of about 6.7 × 103 was found for the value of x = 0.60 at 1 kHz. The ac conductivity followed the Jonscher’s power law, and the conduction was due to the small polaron hopping. The impedance spectroscopy analysis confirmed that both the grains and grain boundaries affected the conduction for samples with x = 0.40, 0.50 and 0.60, while only grain boundary was the dominating factor for the other samples. Polarization-electric field curves (P-E) confirmed that the samples up to x = 0.20 had a good ferroelectric nature with a maximum saturation polarization of 0.34 µC/cm2 and the rest had lossy behavior. The highest magnetoelectric (ME) voltage coefficient was found to be 170 × 103 Vm−1T−1 for x = 0.10.

Structural evolution and multiferroic properties in the vicinity of MPB of Ca2Bi4Ti5-xMnxO18 solid solutions

The crystal structure transition and its effect on the multiferroic characteristics were investigated in Ca2Bi4Ti5-xMnxO18 (0 ≤ x ≤ 2) ceramics synthesized by the molten salt method. Mn substitution induces variations in a/b ratio and the distortion degree of oxygen octahedrons, which can effectively regulate the multiferroic properties at room temperature. The structure changes from orthorhombic B2cb to tetragonal I4/mmm with a morphotropic phase region forming in the ceramic at x = 1.5. The Raman spectra manifest that Mn substitution not only alters the vibration mode of MnO6 octahedron but also changes the structural environment of TiO6 in the perovskite lattice. The average grain size increases gradually and the grain size distribution gets homogeneous with the increase in Mn content. All the ceramics show a lossy dielectric behavior. The addition of Mn results in a significant enhancement in macroscopic magnetization and dielectric properties. In addition to this, the magnetoelectric coupling effect has also been improved and a maximum magnetoelectric coefficient of α ≈ 12.3 mV/(cm·Oe) is attained for the ceramic sample with x = 1.5.