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Composites of barium hexaferrite (BaFe 12 O 19) and nickel zinc ferrite (Ni 0.5 Zn 0.5 Fe 2 O 4) have been prepared by the high-energy planetary ball mill method. The magnetic composites are characterized by employing X-ray Diffraction and High-Resolution Transmission Electron Microscopy (HRTEM) techniques. The percentage of barium hexaferrite (BaFe 12 O 19) and nickel zinc ferrite (Ni 0.5 Zn 0.5 Fe 2 O 4) in the composite has been obtained from the Rietveld analysis of XRD patterns. The average crystallite sizes of BHF and NZFO are found to be comparable in the composites. The magnetic properties of (1-x) BHF-(x) NZFO with x = 0 to 1 have been studied by measuring the magnetic hysteresis loop (M-H loop) for all the samples. The M-H loops are analyzed by plotting the loop width (ΔH) versus magnetization (M). The magnetic hysteresis loops for the BHF and NZFO are found to be symmetric in all the quadrants. However, symmetry breaks in M-H loops for composites. The symmetry breaking in magnetic hysteresis loops of the bi-magnetic composite suggests a new approach to analyzing the magnetic interaction between magnetic phases in the magnetic composites. [ABSTRACT FROM AUTHOR]

In view of tuning different transitions, Co and V are substituted in Mn-rich Ni-Mn-Ga alloy. Ni41Co9Mn30V2Ga18 sample undergoes a coupled magnetostructural transition above room temperature with a low thermal and magnetic hysteresis and high sensitivity of martensite transition temperature (8 K/T) with the field. ∆SM is found to be a maximum of −2.33 J/kg-K for 3 T field change with a large RCP of 158 J/kg. The presence of intermartensite transition along with the magnetostructural transition widens the range of working temperature. [ABSTRACT FROM AUTHOR]

An interfacial integration at the nanoscale domain through a core@shell (CS) nanostructure has constructively unbarred a wide dimension to researchers on biomedical applications, especially for magnetic fluid hyperthermia. Lately, the interconnection of the exchange bias effect (EBE) through the interface coupling to the magnetic heating efficiency has uttered its utmost prominence for researchers. Here, we delineate the ascendency of the heating ability through a coalescing assembly of mixed ferrite Co0.5Zn0.5 Fe2O4 (CZ) and soft magnetic material Fe3O4 (F), by devising a network of CoZnFe2O4@Fe3O4 (CZF) CS nanostructure. A hefty interface activity with validation of the EBE phenomenon is divulged through magnetic scrutiny for the CS sample. The magnetic nanoparticles heating response to applied magnetic field and frequency is discerned at three distinct fields, where the outcome prevailed to inflated specific loss power for CS CZF in distinction to bare F and CZ samples for all the assessments. Remarkably; a lofty intrinsic loss parameter is also perceived for the CS sample recorded to about 5.36 nHm2 g−1; which is another eccentric outcome that significantly labels the CS CZF sample as a potentially high heating competence agent. This comprehension accords to a finer perspective to meliorate the theranostic environment for hyperthermia applications. [ABSTRACT FROM AUTHOR]

The advancement of magnetic materials with coupled magneto-structural phase transition (MST) to fulfill the ultimate objectives of practical solid-state cooling applications requires a better understanding of the hysteresis phenomenon linked across the phase transition region along with the large magnetocaloric parameters. For the present sample Mn0.65Ni0.65Fe0.70Si, the MST is associated with a sharp jump in magnetization along with a small thermal hysteresis of ∼13 K. A giant isothermal magnetic entropy change (| Δ S M max |) of ∼37.6 J kg−1 K−1 at 299 K and effective refrigerant capacity (R C effe ) of ∼214.3 J kg−1 under ΔH = 30 kOe is obtained with excellent compatibility between the martensite and austenite phases. The geometrical compatibility condition, i.e., very small (∼0.55%) deviation of the middle eigenvalue (λ 2) from unity justifies the observation of small hysteresis in the present material. The investigation of hysteresis behavior under different extents of the driving forces (temperature or magnetic field) reveals that both the driving forces trigger equally the phase transition and are responsible equivalently for the hysteresis phenomenon. The present study provides a pathway to understand the complexity of the hysteresis behavior, its impact on the reversibility of magnetocaloric effect, and its minimization by optimizing the geometrical compatibility condition between the austenite and martensite phases. [ABSTRACT FROM AUTHOR]

An interfacial integration at the nanoscale domain through a core@shell (CS) nanostructure has constructively unbarred a wide dimension to researchers on biomedical applications, especially for magnetic fluid hyperthermia. Lately, the interconnection of the exchange bias effect (EBE) through the interface coupling to the magnetic heating efficiency has uttered its utmost prominence for researchers. Here, we delineate the ascendency of the heating ability through a coalescing assembly of mixed ferrite Co0.5Zn0.5 Fe2O4 (CZ) and soft magnetic material Fe3O4 (F), by devising a network of CoZnFe2O4@Fe3O4 (CZF) CS nanostructure. A hefty interface activity with validation of the EBE phenomenon is divulged through magnetic scrutiny for the CS sample. The magnetic nanoparticles heating response to applied magnetic field and frequency is discerned at three distinct fields, where the outcome prevailed to inflated specific loss power for CS CZF in distinction to bare F and CZ samples for all the assessments. Remarkably; a lofty intrinsic loss parameter is also perceived for the CS sample recorded to about 5.36 nHm2 g−1; which is another eccentric outcome that significantly labels the CS CZF sample as a potentially high heating competence agent. This comprehension accords to a finer perspective to meliorate the theranostic environment for hyperthermia applications. [ABSTRACT FROM AUTHOR]

Strontium hexaferrite is a hard magnet that can help to develop rare-earth-free magnets for permanent magnet applications. A composition of SrFe 12-x-y Ni x Al y O 19 (0.005 ≤ x ≤ 0.02; 1 ≤ y ≤ 4) is successfully synthesized with by the sol-gel auto-combustion process, and the effect of Ni-Al substitution is studied on the structural, magnetic, dielectric, and electrical properties. The XRD analysis confirms the formation of magnetoplumbite hexagonal structure with P6 3 / mmc space group. Magnetic studies have shown a massive improvement in the coercivity (H c) of the samples. The highest ever H c value of 24.44 kOe in strontium hexaferrite-based rare-earth free magnet is attained for the SrFe 7.98 Ni 0.02 Al 4 O 19 ferrite composition. The energy density (BH) max is effectively tuned to 16.2 MGOe for the SrFe 8.985 Ni 0.015 Al 3 O 19 composition. The dielectric properties have shown the typical behavior of ferrites and are explained according to the Maxwell-Wagner and Koop model. The proposed work is expected to offer an immense possibility to improve the hard magnetic properties of strontium hexaferrite magnets comparable to the expensive NdFeB magnets in order to fully/partially replace them in different permanent magnet applications. [Display omitted] • An attempt to substitute Ni2+ & Al3+ ions at Fe3+ lattice site in SrFe 12 O 19 ferrite. • Highest ever H c value of 24.44 kOe is attained for SrFe 7.98 Ni 0.02 Al 4 O 19 composition. • Found an enhanced (BH) max value ∼16.2 MGOe for SrFe 8.985 Ni 0.015 Al 3 O 19 composition. • These ferrites offer the utmost probability to use in different PM applications. • This work suggests the exploration of SrM to improve its hard magnetic properties. [ABSTRACT FROM AUTHOR]

• Maximum (BH) max and reduced remanent are found to be 0.887 MGOe and 0.53, respectively, for (50)%BHF+(50)%CFO composite. • Exchange coupling is responsible for enhanced (BH) max and reduced remanent in the composite. • Henkel plot and derivative of magnetization vs field curve are used to explore the magnetic interaction between particles. The (x)% BaFe 12 O 19 (BHF) + (100-x)% CoFe 2 O 4 (CFO) (x = 0 to 100) magnetic composites are prepared to explore its magnetic properties. The XRD patterns reveal the presence of both BaFe 12 O 19 and CoFe 2 O 4 crystal symmetries in the composite. The FESEM and TEM micrographs reveal the uniform distribution of nanoparticles. The theoretical saturation magnetization is calculated by Vegard's law, which is nearly equal to the experimental observation. The maximum reduced remanent (M r /M s) and magnetic energy product (BH) max are found to be 0.43 and 0.456 MGOe, respectively, for x = 50 i.e. (50)% BHF + (50)% CFO. It is explained by assuming magnetic interaction at the interfaces of soft and hard magnetic phases. The coercive field, remannet magnetization, reduced remanent, saturation magnetization, and (BH) max increase with a decrease in measuring temperatures. The enhancement of magnetic parameters at a low temperature is observed due to the decrement of the thermal energy of magnetic moments at the surface. The saturation magnetization increases with an increase in annealing temperature, which could be due to the minimization of spin disorders at the surface of nanoparticles. The enhanced reduced remanent (M r /M s) and (BH) max are found for the (50)%BHF + (50)%CFO composite annealed at a higher temperature. The evidence of magnetic interaction between two magnetic phases in the composite has been realized by employing the Henkel plots and dM dH versus H curve techniques. [ABSTRACT FROM AUTHOR]

• Gadolinium doping in BHF results in modification of magnetic properties. • "Law of Approach to Saturation" gives the magnetocrystalline anisotropy constant. • Para-ferrimagnetic transition is observed around 700 K. • Maximum entropy change and RCP are found to be 0.72 J/kgK and 27.5 J/kg, respectively, near Curie temperature. • Possibility to use the Gd doped BHF at high temperature as a cooling agent. Gd doped barium hexaferrite (BaFe 12−x Gd x O 19 , x = 0.0–0.7) has been synthesized by the sol-gel method to explore its magnetic and MCE (magnetocaloric effect) properties. The materials crystallize to hexagonal magnetoplumbite phase. Average particle size decreases with the increase in Gd concentration in barium hexaferrite (BHF). The coercive field increases from 3.2 to 4.8 kOe, and saturation magnetization decreases from 68.21 to 54.23 emu/g with the increase in Gd concentration from x = 0.0 to x = 0.7. These large changes in magnetic parameters reveal the effect of Gd concentration in BHF. The saturation magnetization monotonously reduces with an increase in Gd concentration in BHF due to a decrease in average particle sizes. The saturation magnetization is found to be higher at a lower temperature (60 K) compared to that of room temperature (300 K). It is due to a reduction in thermal energy at low temperature which is smaller compared to the magnetic Gibbs free energy at low temperature. Hence, the magnetic spins are freezing along the applied magnetic field direction at the low temperature. Also, the magnetocrystalline anisotropy constant (obtained by the "Law of Approach to Saturation method") is found to be more at low temperature compared to that of room temperature due to an increase in the strength of spin-orbit coupling with the decrease in temperature (i.e. thermal energy). The M-T curves and M-H hysteresis loops reveal paramagnetic to ferromagnetic transition at the Curie temperature. The maximum entropy change was found to be in the range of 0.12–0.72 J/kgK in a window of the applied magnetic field of 0.5–3 T, and the corresponding RCP max was found to be 2.5–27.5 J/kg. The present study opens a window to explore the MCE on BHF based material. [ABSTRACT FROM AUTHOR]

With an aim to explore the d0 ferromagnetism in Ag-doped ZnO compounds, the poly-crystalline samples of Zn 1 - x Ag x O (with 0 ≤ x ≤ 0.12) were synthesized by a standard solid-state synthesis technique. The XRD analyses indicated that these compounds have been formed as Ag:ZnO nanocomposite. According to scanning electron microstructural study, all compounds have a homogenous nearly spherical shape morphology. The EDS spectra reveal that the final produced compounds do not contain any unwanted external impurity. The magnetization versus field measurement at room temperature demonstrates that the undoped ZnO compound shows ferromagnetism embedded in diamagnetic matrix, whereas all Ag-doped ZnO samples exhibit a clear room temperature ferromagnetic behavior with coercivity values between 80 and 196 Oe. The maximum saturation magnetization was obtained for the Zn0.97Ag0.03O sample; however, it declines subsequently. The bound magnetic polarons (BMPs) has been considered to explain the observed ferromagnetic behavior. [ABSTRACT FROM AUTHOR]

[Display omitted] • Successful synthesis of PVP capped doped CuS quantum dots. • A marked increase in the band gap of the quantum dots. • Low field magnetic interactions at room temperature. Polyvinlypyrrolidone (PVP) capped and magnetic transition metals (TM = Fe, Co and Cr) doped CuS quantum dots (Cu 1- x TM x S; x = 0.02 & 0.04) were synthesized by low entropy facile chemical co-precipitation method. The structural, optical and magnetic characterizations of the synthesized QDs were done by using X-ray diffraction (XRD) technique, UV–Vis-NIR absorption spectroscopy, photoluminescence (PL) spectroscopy and superconducting quantum interference device (SQUID) respectively. The low field non-linearity and the presence of coercivity in the M−H loops indicate the presence low field magnetic (spin–spin) interactions between the doped cations. [ABSTRACT FROM AUTHOR]

The (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 (0-3 type particulate) nanocomposites with x = 0.00, 0.02, 0.04, 0.06, 0.08, and 1.00 were prepared by the solid-state method. Cobalt ferrite crystallized into cubic crystal symmetry with an F d 3 ̄ m space group. Strontium-substituted barium titanate crystallized into a tetragonal crystal structure with a P4mm space group. Field emission scanning electron microscopy and transmission electron microscopy techniques show the distribution of different sizes of particle. Polarization vs electric field curves show the highest maximum polarization (Pm) of 10.26 μC/cm2, remnant magnetization (Pr) of 11.70 μC/cm2, and coercivity (Ec) of 19.95 kV/cm for x = 0.04 composition at 35 kV/cm. However, it is smaller than the Ba0.8Sr0.2TiO3 phase (Pm = 16.86 μC/cm2, Pr = 13.20 μC/cm2, and EC = 10.80 kV/cm). The highest dielectric constant of around 9800 was found for x = 0.04 composition, with a very small dielectric loss factor of about 0.02, i.e., less than even 2%. This is ∼10 times compared to that of Ba0.8Sr0.2TiO3 (BSTO), which has been explained by considering interaction at the interface of CoFe2O4 (CFO) and BSTO, leakage current, and variation of the lattice parameter of BSTO in (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 nanocomposite. The magnetic hysteresis loops show squeezing near the origin. The magnetic parameters like coercivity, remnant magnetization, and saturation magnetization increased with the increase in the CoFe2O4 weight fraction. Magnetic interaction between surfaces of magnetic CFO and non-magnetic BSTO is evident from the ΔH vs M plots, and it also evidences the magnetism at the surface of BSTO due to uncompensated spins. [ABSTRACT FROM AUTHOR]

Lead-free ferroelectric materials are essential for environment-friendly solid-state cooling technology. In this respect, the electrocaloric effect of lead-free Ba0.8−xSr0.2SmxTiO3 (x = 0.01–0.05) ceramics has been investigated. The Rietveld refinement reveals that all the ceramics exhibit tetragonal symmetry and the tetragonality decreases for x > 0.03, which is the major reason behind the decrease in both isothermal entropy change and adiabatic temperature change. The degree of diffuseness parameter is enhanced by doping of Sm3+, which confirms the formation of polar nanoregion and the enhancement of the electrocaloric effect parameter by adding extra entropy. The relaxor behavior of the prepared samples is also confirmed by estimating the degree of deviation parameter (Δ T m = 77 K ) from the 1 ε r vs. T curve. So, the temperature stability of the prepared ceramics is improved in a broad temperature window. The highest isothermal entropy change (Δ S) , adiabatic temperature change (Δ T) , and electrocaloric strength ( Δ T Δ E ) are found to be 1.230 Jkg−1 K−1, 0.862 K, and 0.028 73 K cm/kV at 316 K, respectively, for Ba0.77Sr0.2Sm0.03TiO3. [ABSTRACT FROM AUTHOR]

Polycrystalline [(0.5) Bi0.5Na0.5TiO3-(0.5) LaFeO3] multiferroic composite is prepared by using the solid-state reaction method. The crystal structure of both phases is characterized by using the X-ray diffraction method (XRD) and confirms the presence of rhombohedral (i.e., bismuth sodium titanate) and orthorhombic (i.e., lanthanum ferrite) phases in the composite. The microstructure of the composite is analyzed using field emission scanning electron microscopy (FESEM). The crystal structure is further studied with Raman spectroscopy. The present composite exhibits ferroelectric and ferrimagnetic-like properties, revealing its multiferroic behavior. Furthermore, the impedance analysis of the composite shows the negative temperature coefficient of resistance behavior. The present study describes the structural and physical properties of the possible lead-free multiferroic composite. [ABSTRACT FROM AUTHOR]

• Sr doped LCMO double perovskite nanoparticles were synthesized using sol–gel method. • Nanoparticles were studied using XRD, TEM, FTIR, Raman, Uv–Vis and M−H curves. • Resistivity curve (R-T) suggest the semiconducting nature for the compound. • M−H and ZFC-FC curves show the interesting magnetic properties of Sr doped LCMO. A study on crystal structure and physical properties has been performed on nanoparticles of lead-free double perovskites, La 2 CoMnO 6 (LCMO) and Sr-doped La 2-x Sr x CoMnO 6 (LSMO:0 ≤ x ≤ 0.08) prepared by the sol–gel synthesis method. In preparation for the LSMO nanoparticle, the La site of the LCMO double perovskite was replaced with an increasing concentration of Sr atom. Structural investigation done by employing the X-ray Diffraction technique indicates that the crystallite size decreases as the doping concentration increases. The Rietveld refinement on the XRD pattern shows the formation of the rhombohedral phase of LCMO (S.G. no. 161). Strain in the prepared samples estimated from Williamson Hall (W-H) analysis shows that the strain decreases as crystallite size decreases. The presence of compressive strain is also evident from the blue shift obtained in the Raman spectrum of the nanoparticles. The UV–Vis spectra reveal the maximum absorption in the near UV region of the electromagnetic spectrum. The Bandgap analysis from Tauc's plot shows an increase in band gap with Sr doping in the LCMO host lattice (from 1.81 eV to 1.92 eV). This is attributed to the decrease in crystallite size and octahedral tilting with Sr doping. Resistivity versus temperature plots reveal the semiconducting nature of the compound. A linear nature graph between l n ρ and T - 1 4 indicates that the electric transport mechanism is governed by the variable range Hopping (VRH) model. The M−H curves show that the maximum magnetization decreases as a result of Sr doping due to the anti-site disorder introduced. dM/dT vs T curve shows two magnetic transitions at ∼ 215 K and at ∼ 173 K which are due to Co2+–O2--Mn4+ and Co3+–O2--Mn4+ ferromagnetic superexchange interactions, respectively. [ABSTRACT FROM AUTHOR]

In the present research work, a conventional solid-state synthesis approach was used to synthesize the polycrystalline compound of Mg-doped ZnO (Zn 1-x Mg x O with x = 0–0.12). The XRD analysis reveals that Mg-doped compounds have been crystallized in a single hexagonal phase. The SEM analysis revealed that these compounds are constituted with microscopic spherical particles with a size range of 1–3 μm. Raman scattering spectra of these compounds displayed a blue-shift of the Raman active E 2 (low) mode attributed to the vibration of zinc atom in wurtzite ZnO, indicating Mg ions were substituted successfully into the ZnO lattice. Optical measurements revealed that the optical band gap enhanced from 3.12 to 3.17 eV, while the transmittance value improved from 87% to 96% as the Mg doping percentage is increased. The magnetization (M) versus applied field (H) measurements, done at 300 K reveals that the undoped ZnO compound exhibits weak ferromagnetic behavior, whereas all Mg-doped ZnO compounds show a strong ferromagnetism with coercivity ranging between 85 O e ≤ H c ≤ 1482 O e , and with the highest saturation magnetization of 0.255 emu/gm for 12% Mg-doped sample. [ABSTRACT FROM AUTHOR]

This study explores the effects of filler concentrations of lanthanum-doped lead zirconate titanate (PLZT) on the electrical and mechanical characteristics of nanocomposite thick film. Crystal structure and morphology of the thick film have been studied using X-ray diffraction, atomic force microscopy, and scanning electron microscopy techniques. It has been noted that adding PLZT nanoparticles to the polyvinylidene fluoride (PVDF) matrix modifies the physical properties of PVDF. In the nanocomposite film, the most prominent polar β phase has been identified at 6 mol% of PLZT filler. In all the films, a nearly homogenous grain distribution has been observed. Frequency-dependent dielectric, conductivity, and impedance of the sample were studied at room temperature. Maximum electric dipole polarization of 0.68 μC/cm2 and piezoelectric (d33) constant of 48 pC/N have been observed at 6 mol% of PLZT filler in the PVDF matrix. Indeed, it has been observed that the (0.94)PVDF–(0.06)PLZT nanocomposite film is well suited for applications such as nanogenerators, structural health monitoring systems, and various kinds of sensors and actuators. [ABSTRACT FROM AUTHOR]

Temperature-dependent dynamic ferroelectric hysteresis of semiconductor–relaxor ferroelectric (0–3) type composite {0.30(ZnO)–0.70[(Bi0.5Na0.5)0.94Ba0.06TiO3 (BNBTO)]} has been investigated using polarization–electric field (P–E) loops, current density–electric field (J–E) curves, and temperature-dependent dielectric permittivity. It is well known that the polarization reversal mechanism can be explained by the concept of ferroelectric domain switching kinetics, which depends strongly on the temperature. The present work ascribes the role of polar nanoregion induced thermal depolarization field on the temperature-dependent ferroelectric hysteresis loop along with polarization reversal mechanism. The present composite exhibits unique ferroelectric switching behavior above the thermal depolarization temperature (∼100 °C), which is observed in P–E and J–E loops. The depolarization field-induced pinched P–E loops of a BNBTO solid solution above Td (∼100 °C) have been significantly overcome by the incorporation of semiconductor (ZnO) particles, which extensively described the underlying mechanism in the present context. In addition, the temperature-dependent polarization reversal mechanism displays unique two-stage processes [low-T (<100 °C) and high-T (>100 °C)] for the minor loops (∼30 and 40 kV) and saturated loops (∼45 kV) as described by the electric field–temperature phase diagram. The present results may provide a distinct way to Bi0.5Na0.5TiO3-based solid solutions for high-temperature piezoelectric applications. [ABSTRACT FROM AUTHOR]

The composites (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 are prepared by solid‐state reaction method using microwave double‐step sintering. Ba0.8Sr0.2TiO3 crystallizes to tetragonal crystal symmetry with P4mm space group and CoFe2O4 crystallizes to cubic crystal symmetry with Fd3¯m space group. Electron microscopy techniques are used to understand the microstructure, elemental composition, and morphology of the composites. The dielectric properties are measured in the 1 Hz–1 MHz frequency range and 40–400 °C temperature range. Composite with x = 0.1 (ε′ ≈ 170, tan δ = 0.08 at 1 kHz) and 0.2 (ε′ ≈ 390, tan δ = 0.07 at 1 kHz) has better dielectric properties than the parent Ba0.8Sr0.2TiO3 ferroelectric (ε′ ≈ 125, tan δ = 0.16 at 1 kHz) and CoFe2O4 ferrimagnetic phases (ε′ ≈ 375, tan δ = 0.72 at 1 kHz), respectively. Composite with 10% cobalt ferrite has the highest saturation polarization (2.1 μC cm−2), the highest remanent polarization (0.9 μC cm−2), and coercive field (23.9 kV cm−1) compared to ferroelectric phase followed by x = 0.2 composite (PS = 1.6 μC cm−2, Pr = 0.8 μC cm−2, and EC = 19.2 kV cm−1). Composite with x = 0.2 shows the highest magnetic coercive field of 1.96 kOe. Hence, this article advocates that 20% ferrite in the composites is the optimized composition for multiferroic applications. The present study will help to explore piezoelectric, magnetostrictive, and magnetoelectric properties of (x)CoFe2O4–(1−x)Ba0.8Sr0.2TiO3 for the technological application. [ABSTRACT FROM AUTHOR]

The analysis of structural, electrical transport, critical magnetic behavior, and magnetocaloric properties of Co2CrAl Heusler alloys has been conducted here. Co2CrAl full Heusler alloy has been prepared by the conventional arc melting method in Ar atmosphere and post‐annealing in a vacuum‐sealed quartz tube. X‐ray diffraction (XRD) pattern reveals the crystallization of the alloy to the Fm3¯m space group with L21 crystal symmetry. The correspondence between the magnetic and electrical transport properties of the Co2CrAl alloy has been observed. This alloy exhibits paramagnetic to ferromagnetic transition (Curie temperature) just above room temperature at around 340 K. Metallic to semiconducting transition occurs near the magnetic Curie temperature. Critical magnetic behavior has been analyzed by employing the Arrott plot, Kouvel–Fisher methods, and critical isotherm analysis. These conclude that the exchange interaction in Co2CrAl alloy follows between mean‐field theory having spin–spin long‐range interaction and the 3D Heisenberg model. The magnetocaloric effect has been explored from the isothermal magnetization data by employing Maxwell's equations. The highest magnetic entropy change is found to be ≈0.99 J (kg K)−1 for a magnetic field change of 30 kOe. A large working temperature window of 57 K is the advantage of the present alloy. [ABSTRACT FROM AUTHOR]

An attempt has been made here to synthesized ceria (CeO2) and Ce0.80Zr0.20−xAxO2 (A = Fe, Co; x = 0–0.20) powders via novel sol–gel technique using metal nitrate hydrates as precursors and distilled water and ethanol as solvents. The resulting gel was dried at 130 °C for 24 h and calcined successively at 850 and 950 °C for 3 h each. Ceria is shown to exhibit a fluorite-type cubic structure with a slightly higher lattice parameter a = 5.428 Å, Z = 4, space group Fm 3 ¯ m , some Ce3+ ions and oxygen vacancies. 20% zirconium substitution of cerium causes decrease of ‘a’ to 5.395 Å owing to a lower ionic radius of Zr4+ vis-à-vis Ce4+. However, the lattice parameter first increases and then decreases with partial/ full replacement of Zr4+ by cobalt or iron ions. Evidence is found for existence disorder/strain, mismatch of ionic radii and oxidation states of cations, and appropriate oxygen vacancies to ensure charge neutrality of systems. The photoluminescence (PL) spectra reveal peaks at ~ 371, 402, and 432–445 nm, which are attributed to Ce 4f0 → 4f1 direct transition, Ce 4f0 → 4f1 electron transfer via oxygen F++ state, and oxygen vacancies (excited oxygen F+* → F+ transition), respectively. Their Raman spectra display a peak at ~ 462 cm−1 due to F2g symmetric vibrations of a cubic CeO8 sub-cell with some variation in position and sharpness with/without a signal in the range 150–170 cm−1 by introduction of different cations leading to distortion and formation of anion vacancies. [ABSTRACT FROM AUTHOR]

Ferroelectric perovskites materials are the most promising materials because of their multifunctional applications as well as the ongoing fundamental research on them. The present study investigates the correlation between the crystal structure and various physical properties such as dielectric, ferroelectric, and optical properties of Sr2+ modified Sodium bismuth titanate Na 0.5 Bi 0.5−x Sr x TiO 3 (x = 0.00, 0.02, 0.04, and 0.06) synthesized by solid-state reaction method. Rietveld refinement of the X-ray diffraction pattern reveals that the system undergoes a crystal symmetry transition from a two-phase crystal symmetries system (rhombohedral (R3c) and tetragonal (P4bm)) to a three-phase crystal symmetries system (rhombohedral (R3c), tetragonal (P4bm) and Cubic (Pm 3 ̅ m)) with the rise in Sr2+ concentration in Na 0.5 Bi 0.5−x Sr x TiO 3 which is the foremost reason behind the variation of physical properties of the system. The dielectric constant and maximum polarization increase with the Sr2+ concentration up to 2% and it decreases with the further increase in Sr concentration due to the distortion in crystal structure induced by the introduction of cubic phase (Paraelectric) in the system. The maximum value of the dielectric constant is estimated to be 3629 at a low frequency on the Na 0.50 Bi 0.48 Sr 0.02 TiO 3 system. The optical band gap (E g) of Na 0.5 Bi 0.5−x Sr x TiO 3 (x = 0.00, 0.02, 0.04, and 0.06) ceramics are found to vary between 3.202 eV to 3.172 eV which indicates the semiconducting nature of prepared samples but urbach energy shows an opposite behaviour i.e. increases with Sr concentration. [Display omitted] • Crystal symmetry transition occurs from R3c + P4bm to R3c + P4bm + Pm 3 ̅ m. • Na 0.50 Bi 0.48 Sr 0.02 TiO 3 exhibits Maximum polarization of 7.05 μC/cm2. • The highest dielectric constant is found to be 3629 for Na 0.50 Bi 0.48 Sr 0.02 TiO 3. • Na 0.50 Bi 0.48 Sr 0.02 TiO 3 ceramics exhibits a low optical band gap of 3.138 eV. • Sr2+ modified NBT can be utilized in various technological applications. [ABSTRACT FROM AUTHOR]

• Overall magnetic properties depend on phase evolution. • Average particle size increased with increasing annealing temperature. • Transition from single-domain to multi-domain configuration with annealing. • Incoherent magnetization reversal mechanism in single domain Ba 1-x Sr x Fe 12 O 19. The correlation of phase evolution (annealing at different temperatures) with magnetic properties like magnetization reversal, coercivity mechanism, and energy product in M-type hexaferrite by substituting Sr in place of Ba has been reported in the present article. The Ba 1-x Sr x Fe 12 O 19 (x = 0.0, 0.5, & 1.0) have been prepared by the sol–gel auto-combustion method followed by annealing at different temperatures from 800 °C to 1200 °C. The structural and magnetic properties have been characterized by X-ray diffraction, Field emission scanning electron microscopy, Raman spectroscopy, and Vibrating sample magnetometer. The Rietveld refinement confirms contraction in unit cell parameters by replacing Sr in place of Ba and lattice expansion with increasing annealing temperature. There is no significant effect of substitution on magnetic properties found rather heat treatment affects greatly. The transition from a single domain to multidomain particles and their contribution to initial magnetization curves are analyzed. The differential susceptibility (dM/dH) calculated from room temperature magnetization confirms the existence of a pinning effect during magnetization reversal for samples heat treated below 1200 °C. Secondary phases or grain boundaries are believed to act like pinning centers. This work opens insight into the domain wall motion by microstructure engineering. The coercivity is tuned to 6.09 kOe by controlling the annealing temperature for the Ba 1-x Sr x Fe 12 O 19 (x = 1.0) sample. The maximum energy product (BH) max in the range of 0.94–1.27 MGOe has been achieved. [ABSTRACT FROM AUTHOR]

Structural, optical, temperature dependent magnetic and electrical properties have been investigated for the nanocrystalline NiFe 1.97 RE 0.03 O 4 (RE = La3+ and Sm3+) compound. Without any signs of a secondary REFeO 3 phase, the Rietveld refinement reveals a single-phase spinel structure possessing cubic symmetry for current samples. The decrease in lattice constant has been observed as a result of RE ions substitution. The TEM micrographs reveal nanosized particles with an average size of 35 ± 3 nm and 32 ± 3 nm for La3+ and Sm3+ substituted samples. EDX spectra of both samples show good compositional homogeneity. HRTEM micrographs of both samples show well resolved lattice fringes and their inter-planar spacing matches with that obtained from the Rietveld analysis of the XRD patterns. The concentration of Fe2+ and Fe3+ ions has been estimated from the XPS spectra analysis and it is found to be ∼ 22% and 78% for NiFe 1.97 La 0.03 O 4 and, 20% and 80% for NiFe 1.97 Sm 0.03 O 4 compound. The optical energy band gap for rare earth substituted samples is found to be more than that of pure nickel ferrite. The value of saturation magnetization (M s) and magneto-crystalline anisotropy constant (K 1) estimated from the "Law of Approach to Saturation" equation for rare earth substituted samples are found to be less than that of pure nickel ferrite. However, an enhanced value of coercivity has been observed with RE substitution. ZFC (zero field cooling) and FC (field cooling) DC magnetization curves measured at 100 Oe in the temperature range of 60–400 K reveal a combination of weak and intermediate forms of magnetic interaction between the particles for both samples. Temperature dependent analysis of saturation magnetization and coercivity employing modified Bloch's law and Kneller's relation supports the nanomagnetic behavior of both samples. Under an AC magnetic field of 14.92 kA/m and frequency 337 kHz, the SAR and ILP values have been found to be ∼ 331 W/g and 4.22 nHm2/kg for NiFe 1.97 La 0.03 O 4 and, ∼ 241 W/g and 3.21 nHm2/kg for NiFe 1.97 Sm 0.03 O 4. The dielectric relaxation data have been analyzed at various temperatures ranging from 40 to 300 0C over the frequency range 100 Hz-1 MHz using electrical impedance spectroscopy. The dielectric constant for rare earth substituted samples is found to be more and their AC conductivity is observed to be less than that of pure nickel ferrite. The analysis of temperature dependent AC conductivity employing Jonscher's power law suggests that the charge carrier's conduction mechanism of both samples follows the small polaron hopping mechanism below 200 0C, thereafter; it follows the correlated barrier hopping mechanism. The activation energy estimated by imaginary impedance spectra is found to be 0.411 eV and 0.398 eV for NiFe 1.97 La 0.03 O 4 and NiFe 1.97 Sm 0.03 O 4 which is more than that of pure nickel ferrite. The Cole-Cole plots at different temperatures suggest the presence of non-Debye-type relaxation. The modeling of Cole-Cole plots with equivalent circuits for both samples confirms the contribution of both grain and grain boundary in electrical conduction. The estimated stretching exponential factor by fitting the modified KWW (Kohlrausch-Williams-Watts) equation to the imaginary modulus curve reveals relatively more dipole-dipole interaction in NiFe 1.97 Sm 0.03 O 4 than that of the La3+ substituted sample. [Display omitted] • Samples crystallized to single phase cubic spinel structure with F d 3 − m space group. • ZFC-FC analysis reveals intermediate type magnetic interaction between particles. • SAR is estimated by initial slope, Box-Lucas and modified Newton cooling approach. • Nyquist plots reveal non-Debye type dielectric relaxation and NTCR type behavior. • Presence of considerable induced dipole-dipole interaction in current samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • The fabrication of an efficient lead-free three-phase nanocomposites as a PENG. • A remarkable ε r (∼44) is achieved by incorporating BSTO and CNT fillers in PVDF. • PENG device yields 9 µA high output current and 31.5 µW high output power. • PENG device exhibits analog and digital switching with a high I ONN/OFF ∼7×102. • NG-PB0.20 device's photoactive response highlights its use in optoelectronics. Nowadays self-charging memristors and photodetectors open the path for future research into energy-autonomous electronics which hold the promise of enabling exceptionally efficient applications in memory storage, small portable electronics, neuromorphic computing, and optoelectronics devices. Hence, in the recent era, much research work has been focused on the development of nanogenerators for technological applications. In this regard, the main aim of the present study is to develop a multi-functional piezoelectric nanogenerator based on relaxor ferroelectric materials having three-phase MWCNTs/BSTO/PVDF nanocomposites. BSTO and CNT fillers promote >80 % electroactive phase nucleation in PVDF, making it appropriate for piezoelectric energy harvesting devices. Incorporating conductive fillers (CNTs) and dielectric fillers (BSTO) into the PVDF matrix enhances the piezoelectric nanogenerator's dielectric, ferroelectric, and output performance. PENG based on an optimized BSTO-CNTs-PVDF composite (with 20 % BSTO and 0.20 % CNTs loading) produced an output power of 31.5 µW with a high open-circuit voltage of 42 V and a short-circuit current of 9 µA, it demonstrates enough capability to power up small portable electronic devices. This work can also be used for a realistic technique for generating self-powered memristors and photodetectors for extremely efficient memristive neural networks and optoelectronics devices. Demonstration of power generation of the prepared device by different activities is demonstrated. [ABSTRACT FROM AUTHOR]

Nickel-Manganese-Gallium-based Heusler alloys have been extensively studied for magnetic cooling applications with different compositions. However, the large hysteresis and narrow range of working temperatures associated with the first-order phase transition make limit their practical application. In this direction, the magnetocaloric effect was analyzed for three different off-stoichiometric compositions of Ni 50+y+z Mn 25+x-y Ga 25‐x‐z alloys, where x, y, and z vary once at a time. Ni 50 Mn 27 Ga 23 (NMG 1) and Ni 54 Mn 21 Ga 25 (NMG 2) samples show large magnetocaloric effects across the second-order ferromagnetic to paramagnetic phase transition. Another sample Ni 54 Mn 25 Ga 21 (NMG 3) undergoes coupled magneto-structural transition near room temperature with very low hysteresis loss (⁓4 J/kg) and a very high sensitivity of the martensite transition temperature (⁓3.6 K/T) with the field. By cyclic cooling protocol reliable magnetic entropy changes are found to be maxima of − 1.98 ± 0.09, − 1.90 ± 0.11 and − 3.53 ± 0.14 J/kg-K for 3 T field change with large effective RCP values of 235.8 ± 0.1, 161.5 ± 0.1 and 144.7 ± 0.3 J/kg for NMG 1, NMG 2 and NMG 3, respectively. The presence of inter-martensite transition along with the magnetic transition or magneto-structural phase transition widens the range of working temperature which effectively enhances the magnetic cooling performance of these materials. The T C and T M are tuned in Ni-Ga-Mn-based alloys by changing the chemical composition with considering the electron concentrations. • Large magnetocaloric effect on Ni 50+y+z Mn 25+x-y Ga 25‐x‐z Heusler alloys. • Hysteresis free large MCE on Ni 50 Mn 27 Ga 23 and Ni 54 Mn 21 Ga 25. • Reliable MCE by cyclic cooling across magneto-structural transition on Ni 54 Mn 25 Ga 21. • Low hysteresis loss and high sensitivity of the martensite transition temperature. • Wide working temperature due to the presence of inter-martensite transition. [ABSTRACT FROM AUTHOR]

The (0.90)Y2O3:(0.10-x)Eu3+:(x)Bi3+ nanophosphors (0.00 ≤ x ≤ 0.06) are synthesised using chemical combustion citrate route and characterized via X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, UV- visible and photoluminescence spectroscopy. The scanning electron micrographs indicate that the grain size of the phosphors ranges between 40 to 50 nm. The photoluminescence (PL) spectra, acquired under the excitation wavelength of 365 nm of ultraviolet light, show emission peaks at wavelengths 580 nm, 586-598 nm, 610 nm, 629-661 nm and 686-695 nm corresponding to the 5D0 → 7FJ electronic transitions of the Eu3+ ion with J = 0, 1, 2, 3 and 4, respectively. The most intense PL spectra at 611 nm (5D0 → 7F2), showcasing reddish-orange emission, indicate a higher concentration of Eu3+ ions in asymmetric sites within the Y2O3 host matrix. The presence of the distinct electronic transitions of Eu3+ in PL spectra acclaims that Bi3+ ions transfer their energy efficiently to Eu3+ ions in the matrix. Physical and chemical tests are being conducted on nanophosphors with Bi3+ substitutional doping of x = 0.02 and x = 0.04, both demonstrating intense PL emission. Magnetisation measurements suggest the soft magnetic nature of the nanophosphors, attributing it to the presence of Eu3+ ions in the 7F2 state. The highest PL intensity is seen in the nanophosphor (x = 0.04) with substitutional doping of 6% of Eu3+ and 4% of Bi3+ in Y2O3. This nanophosphor also demonstrates excellent optical stability in the investigated conditions and exhibits soft magnetic behaviour, positioning it as a promising material for incorporation as a fluorescent magnetic pigment in security ink applications. These features serve to prevent counterfeiting of secured documents both optically and magnetically. [ABSTRACT FROM AUTHOR]

Al-substituted strontium hexaferrite (SrFe 12-x Al x O 19) has been synthesized by the sol-gel auto-combustion method, followed by microwave sintering at 1100 °C. The Rietveld refinement of XRD patterns reveals the hexagonal crystal symmetry with P6 3 /mmc space group. Lattice contraction has been observed with the increasing Al3+ concentration in SrFe 12-x Al x O 19. The anisotropy field is found to be ∼25 kOe for SrFe 11·5 Al 0·5 O 19. The (BH) max (maximum energy product) of 1.20 MGOe is obtained for x = 0.0 whereas there is a 63.66% enhancement of coercivity for SrFe 11·5 Al 0·5 O 19 at 300 K. However, the highest (BH) max of 1.84 MGOe has been achieved at 60 K for SrFe 11·5 Al 0·5 O 19. The criterion for a permanent magnet is satisfied by analyzing the hardness parameter. All the samples are found to be magnetically hard with (BH) max in the range (1.00–1.20) MGOe at 300 K. • Lattice contraction in SrFe12-xAlxO19 (0≤x≤0.5) • All the synthesized samples are magnetically hard • Enhancement of anisotropy field up to 25 kOe • Uniform magnetic interaction confirmed by ΔH vs M plot • Highest (BH)max of 1.84 MGOe achieved for SrFe11.5Al0.5O19 at 60 K [ABSTRACT FROM AUTHOR]

Magnetic materials with reversible magnetocaloric effect across their respective first-order magneto-structural transitions (MST) have vital significance for further advancement towards the ultimate goal of practical magnetic cooling applications. In this present study, the reversibility of the MST is investigated by analyzing the isofield curves under different minor and major thermal hysteresis loops and the isothermal curves under different magnetic field cycles. The reversibility of the magnetocaloric effect (MCE) depends upon the width of the nucleation energy barrier existing across the MST. Minor hysteresis loops are found to be minimizing the energy loss by preventing the nucleation of the martensite phase and can be easily returned to the austenite phase immediately while switching from cooling to heating. A large reversible isothermal magnetic entropy change Δ S M of −14.4 J kg−1 K−1 nearly at 322 K is observed for the (Mn 0.45 Fe 0.55) (Ni 0.6 Co 0.4) Si alloy under a low magnetic field change of 3 T. The observed large reversible MCE, very low magnetic field-induced hysteresis loss, and large reversible RC effe ∼ 155 J kg−1 will be beneficial for reducing the energy loss during several magnetic field cycles in practical cooling applications which makes this alloy promising for the development of efficient magnetic refrigerants. • Largest reversible Δ S M ∼ -14.4 Jkg−1K−1 is observed in Mn-Ni-Si based alloys for Δ H ∼ 3 T. • Minor hysteresis loops minimize the negative impact of thermal hysteresis on MCE. • Overlapping nature of successive M-H cycles confirm the reversibility of MCE. • Large sensitivity (2.75 KT−1) of MST helps to obtain a large Δ S tr ∼ 38.2 Jkg−1K−1. [ABSTRACT FROM AUTHOR]

• Barium hexaferrite (BHF) film on Si substrate deposited by pulse laser depositions. • BHF film has very less coercive field compared BHF nanoparticle. • Magnetic parameters are directional dependent. • Magnetic bifurcation is observed in the film as well as powder due to magnetic frustration. The thin film of BaFe 12 O 19 (BHF) on a silicon substrate has been prepared by the pulse laser deposition method. The crystal structure, morphology, elemental analysis, and magnetic properties have been investigated by using X-Ray Diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy, elemental dispersive x-ray analysis, and vibrating sample magnetometry, respectively. The Rietveld refinement of XRD patterns of BHF powder has been performed to study the crystal structure and lattice parameters. Peak shifting in XRD pattern and Raman spectra for the thin film have been observed compared to that of powder sample. It could be due to the existence of stress at the interface of film and substrate. The magnetic hysteresis loops (M-H loops) of BHF thin film and powder were traced at 60 K and 300 K. The M-H loops of BHF suggest the hard and soft magnetic nature of powder and thin film, respectively. There is a large difference has been observed between saturation magnetization measured by applying a magnetic field parallel and perpendicular directions of the thin film. The bifurcation in zero field cooling (ZFC) and field cooling (FC) magnetization curves reveals the magnetic frustration in the thin films. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties have been investigated in the magnetic composites of hard magnetic Barium hexaferrite (BHF) and soft magnetic Ni–Mn–Sn Heusler alloy. The magnetic composites undergo two distinct ferromagnetic to paramagnetic and ferrimagnetic to paramagnetic phase transitions corresponding to alloy and BHF phases, respectively. Magnetic biasing between the hard and soft magnetic phases has been observed in the composites when both the phases are in the ferromagnetic ordering i.e., a squeezing in the magnetic hysteresis curve is observed around H = 0. The squeezing effect may be used in the magnetic memory device application where an optimum coercivity, high remanent magnetization, and high squareness ratio are required. On the other hand, the composites show high magnetocaloric effect with a constant high value of magnetic entropy changes between the two successive magnetic transitions. This gives an advantage with wide working temperature in the magnetocaloric application. • Magnetic composite of soft magnet Ni 1.8 Mn 1.2 Sn and hard magnetic BaFe 12 O 19. • Magnetic biasing i.e., a squeezing in the M-H curve around H = 0. • Squeezing effect in the magnetic memory device application. • Constant high magnetic entropy changes between the two magnetic transitions. • Potential material for magnetocaloric application with wide working temperature. [ABSTRACT FROM AUTHOR]

Researchers have been making persistent efforts in recent years to find novel and suitable oxide materials with room temperature d0 ferromagnetic characteristics to be utilized in spintronics devices. The fundamental goal of this work is to investigate the effect of K/Mg co-doping on the structural, magnetic, optical, and transport (dielectric and Hall Effect) properties of Zn 0.94−y K 0.06 Mg y O compounds produced via solid-state process (y = 0, 0.02, 0.04, 0.06, 0.08). The X-ray diffraction pattern examination of these compounds revealed their hexagonal wurtzite structure. The Raman spectrum also displays the hexagonal wurtzite structure of ZnO without any lattice disorder. The elemental colour mapping demonstrates that all of the elements are dispersed uniformly throughout the compound. The concentration of K/Mg co-doping was increased, and this resulted in an improvement in the dielectric value and ac conductivity. Moreover, low dielectric loss in these compounds is observed and thus projecting it as a potential material to be utilized in high-frequency optoelectronic devices. The analyses of Nyquist plots show that higher Mg co-doping results in an increase of non-Debye kind relaxation and it led to a decrease in the grains and grain boundaries resistance. According to the analysis of dielectric data using the Maxwell-Wagner model, hopping of charge carriers are likely to be responsible for the electrical transport. As revealed from optical property measurement, the band gap was found to be slightly altered and the transmittance value increased from 82% for Zn 0.94 K 0.06 O to 86% for K/Mg co-doped ZnO compounds. The Hall Effect investigation clearly indicated p-type conductivity and enhanced carrier density concentration. Furthermore, it has been discovered that these substances exhibit ferromagnetism at room temperature. [Display omitted] • Zn 0.94 −y K 0.06 Mg y O compounds were synthesized by the solid-state reaction method. • Optical band-gap narrowing, p-type conductivity and carrier concentration enhancement was observed with the increase of Mg doping concentration. • The transmittance value increased from 82% for Zn 0.94 K 0.06 O to 86% for K/Mg co-doped ZnO compounds. • The dielectric constant and ac conductivity were found to increase with Mg-doping concentration. • Room temperature d 0 Ferromagnetism has been observed in all compounds. [ABSTRACT FROM AUTHOR]

The Na-doped TiO 2 compounds, i.e Ti 1 − x Na x O 2 0 ≤ x ≤ 0.12 were synthesized via the solid-state synthesis method. The formation of single rutile phase with tetragonal structure was identified through the structural study by recording the XRD patterns. The analyses of the XRD patterns further indicate that Na+ ions are likely being substituted at the interstitial site of Ti4+ ions. The microstructural study using SEM revealed the homogeneous morphology of all compounds, with the particle size in the range of 1–2 μ m. The room temperature magnetization versus field measurement reveals a ferromagnetic behavior for all Na-doped compounds with coercivity values ranging from 100 to 930 Oe. The saturation magnetization was observed to be maximum for Ti 0.97 Na 0.03 O 2 compound but thereafter it decreases. According to optical property measurements, the bandgap reduces from 2.94 to 2.71 eV as the concentration of Na doping increases. The maximum transmittance value 91% was noted for Ti 0.97 Na 0.03 O 2 compound. The Hall effect measurements indicate that the carrier concentration of all Na-doped TiO 2 ranged from 1.077 × 10 15 to 7.579 × 10 15 /cm3, and it grew monotonically with the increase of Na-doping concentration. The value of the ac conductivity and dielectric constant were observed to enhance with increasing Na-doping concentration; indicating that transport occurs via hopping of the charge carrier. Further, the dielectric properties observation reveals lossless nature in the produced sample, which suggests that this material could be employed in high-frequency optoelectronic devices. [Display omitted] • Room temperature d 0 Ferromagnetism has been observed in Na-doped rutile TiO 2 compounds. • Hysteresis loops with a maximum saturation magnetization of 0.038 µ B per Na-ion was observed for 3% Na-doped compound. • Optical band-gap narrowing and carrier concentration enhancement was observed with the increase of Na doping concentration. • Very high optical transmittance value i.e., 83% (for TiO 2) to 91% (for 3% Na-doped TiO 2) was observed. • Zero dielectric loss was observed for all Na-doped compounds. • The dielectric constant and ac conductivity were found to increase with Na-doping. • These materials can be used for potential application for spintronics and optoelectronics devices. [ABSTRACT FROM AUTHOR]

• Martensite transition (MT) near the room temperature (RT) was observed. • Giant magnetocaloric effect (MCE) in Ni 45 Mn 44 Sn 11-X In X was observed near RT. • Increase in MT temperature with increase in In concentration was observed. • High value of magnetic entropy change and refrigerant capacity were achieved. • Unit cell volume effect is responsible for the increased MT temperature and MCE. Here, we report the first order martensite to austenite transition characterized through magnetic and calorimetric studies in (off-stoichiometric) shape memory Heusler alloy Ni 45 Mn 44 Sn 11-X In X (X = 1; 3) in the proximity of room temperature. The structural properties of the alloys were checked with x-ray diffraction (XRD), x-ray photoemission spectroscopy (XPS) and energy dispersive x-ray analysis (EDXA). The dominance of a particular phase (martensite or austenite) at room temperature can be predicted from the structural study by XRD as two different phases (L2 1 and 10 M) were found at room temperature with different proportion for the two alloys. Martensite transition was observed near the room temperature for both samples which was monitored with differential calorimetry and magnetization study. A large magneto-caloric effect was found in the system near the room temperature observed from the magnetic measurements. The calculated entropy change (3.24 JKg−1K−1 and 11.2 JKg−1K−1 for X = 1 and 3 respectively) and the refrigerant capacity (27 JKg−1 and 40 JKg−1 for X = 1 and 3 respectively) for 3 T magnetic field were found to be significant for practical applications near room temperature. A small amount of In substitutions in Sn sites have influenced the martensite transition as a significant increase in the martensite transition temperature has been observed. The magnetocaloric effect in these materials has been understood in the realm of sharp magnetization change arising in the vicinity of metamagnetic transition from the martensite phase (weakly magnetic) to the austenite phase (ferromagnetic). The In substitution is thought to influence the hybridization between Ni-Mn bonds which in turn influence the martensite transition and thereby enhancing the magnetocaloric property of the materials. [ABSTRACT FROM AUTHOR]

The large electrocaloric effect associated with the ferroelectric-relaxor and ferroelectric-paraelectric phase transition, and various temperature dependent scaling behaviours on A-site modified BaTiO 3 (Ba 1-x Sr x TiO 3 , x = 0.00, 0.10, 0.20, and 0.25) have been reported in this article. The compositionally induced relaxor behaviour with diffuse phase transition has been reported. The Rietveld refinement of XRD patterns reveals that all the samples crystallize to the P4mm space group. Raman spectra analysis at room temperature supports the XRD patterns analysis. The diffuse phase transition behaviour of the prepared sample has been confirmed by estimating the diffuse phase parameter (γ = 1.444 ± 0.003) from the temperature variation dielectric plot. A large adiabatic temperature change (Δ T) of 0.278 K and isothermal entropy change (Δ S) of 0.494 J/kgK have been observed for the sample x = 0.20 (Ba 0.8 Sr 0.2 TiO 3) at 338 K. The temperature dependent scaling relation for remnant polarization (P r), coercive field (E c), and hysteresis area < A > are found to be P r ∝ T − 1.009 , E c ∝ T − 1.890 and < A > ∝ T − 1.169 , respectively. The present comprehensive studies on A-site modified BaTiO 3 illustrate the electrocaloric cooling efficiency of this material. • Significant adiabatic temperature change (Δ T) of 0.278 K on Ba 0.8 Sr 0.2 TiO 3. • Significant isothermal entropy change (Δ S) of 0.494 J/kg K on Ba 0.8 Sr 0.2 TiO 3. • Polar-nano region (Relaxor ferroelectric signature) near the room temperature. • Diffuse phase parameter (γ =1.444) reveals the diffuse phase transition behaviour of Ba 0.8 Sr 0.2 TiO 3. • The scaling relations are P r ∝ T − 1.009 , E c ∝ T − 1.890 , and < A > ∝ T − 1.169 . [ABSTRACT FROM AUTHOR]

• Atomic distribution is Fe 2.5 Mn 0.5 Al which is crystallized in B 2 phase of the Fm 3 ¯ m space group. • Curie temperature is at 280 K. Magnetic and Electrical phase transitions are occuring here. • Near room temperature this sample exhibit semiconducting nature of resistivity. • It is observed that there is a correlation between magnetic ordering and various temperature dependent scattering phenomena of electron. • The critical exponents are β = 0.48, γ = 1.11, and δ = 3.1. So, long range spin ordering is existing in the sample. The Fe 2.5 Mn 0.5 Al Heusler alloy, prepared by Arc melting method, crystallizes to B 2 in the Fm-3m space group. Resistivity measurement shows semi-metallic behavior in low temperature due to the dominance of magnon-magnon scattering and, exhibits semiconducting nature above the Curie temperature. Hence, it is predicted that there is a correlation between magnetic ordering and electrical transport properties. Arrott plot, Kouvel fisher method, and Widom scaling relation have been used here to determine the critical exponents. The Curie temperature (T C) is found to be near room temperature at 280 K. Also, critical exponents indicate that the magnetic ordering is following mean-field theory i.e., long-range interaction is present with 2nd order para to ferromagnetic transition. On the other hand, due to the 2nd order magnetic phase transition, significant magnetocaloric effect has been observed in a wide temperature range near room temperature. The maximum entropy change is found at 280 K i.e., at Tc. [ABSTRACT FROM AUTHOR]

The present work emphases on the structural, elemental, magnetic, optical, and electrical transport properties of Zn 1-x K x O (0 ≤ x ≤ 0.12) compounds for their plausible application in spintronic devices. These compounds have been crystallized in a single phase and formed with spherical particles of size 3–6 μm. At 300 K, the M − H curve reveals that undoped ZnO exhibits diamagnetism but all K-doped ZnO compounds show M − H hysteresis loops similar to ferromagnetic material with coercivity in the range of 80–140 Oe. These compounds exhibit maximum saturation magnetization of 0.04 μ B per K-ion for 6% K-doped compound. The optical band gap values of the prepared compounds are reduced as the K concentration increases. The value of transmittance was observed to enhance from 87% (for ZnO) to 92% (for 9% K-doped ZnO) sample. The Hall effect study reveals that all K-doped ZnO samples exhibit p-type nature and the carrier density (hole) increases with the increase of K concentration. [ABSTRACT FROM AUTHOR]

• Nanocrystallite size effect on structure and magnetic properties of Ni 1.8 Mn 1.2 Sn. • Presence of both full Heusler L2 1 and inverse Heusler XA crystal symmetries. • The sample can be treated as a natural composite of Ni 2 MnSn and Mn 2 NiSn. • Magnetization not following a linear relation with volume fraction of each phase. • Antiferromagnetic coupling between the two phases. • Magnetization value further decreases for ball-milled nanocrystalline sample. • The magnetic ordering in bulk sample follows mean field theory. • For nanocrystalline sample, the magnetic ordering is a short-range type. The effect of nanocrystallite size on crystal structure and magnetic properties of off-stoichiometric Ni 1.8 Mn 1.2 Sn Heusler alloy has been investigated. XRD (X-Ray Diffraction) and HRTEM (High-Resolution Transmission Electron Microscopy) analysis revealed the presence of both the full Heusler (Ni 2 MnSn) L2 1 and inverse Heusler (Mn 2 NiSn) XA crystal symmetries. Hence, the sample can be treated as a natural composite of both phases. However, the magnetic analysis reveals that the magnetization does not follow a linear relationship with the volume fraction of the individual phases. Rather, the antiferromagnetic coupling between the two phases may be responsible for lowering the net magnetization. On the other hand, magnetization value further decreases for ball-milled sample (nanocrystallite size). Critical magnetic behavior analysis reveals that the magnetic ordering in bulk sample follows mean field theory, and for nanocrystalline sample, the magnetic ordering is a short-range type. [ABSTRACT FROM AUTHOR]

Nickel ferrite fiber (NFO–F) was synthesized using the electrospinning technique and annealed at five different temperatures (500, 600, 700, 800, and 900 °C) to study its effect on crystal structure and magnetic properties. The X-Ray diffraction pattern analysis was carried out to explore its crystal structure. The morphology and microstructure of fibers were studied by employing the Field Emission Scanning Electron Microscopy technique. The crystallinity of the material increases with the increase of annealing temperature from 500 to 900 °C. The saturation magnetization of nickel ferrite fiber increases from 31.1 to 54.0 emu/g with the increase in annealing temperature. The anisotropy constant for NFO–F calculated using the Law of Approach to Saturation (LA) and it shows the highest value for 900 °C annealed sample. Hence, the hyperthermia property of NFO–NF annealed at 900 °C has been explored. The Specific Absorption Rate (SAR) of NFO–NF calculated using Linear Response Theory and the Box-Lucas models. • Fabrication of nickel ferrite nanofiber by Electrospinning method. • The study of magnetic properties by M-H and M-T curve analysis. • Nickel ferrite nanofiber annealed at 900° C suitable for Hyperthermia application. • LR theory and B-L model are used for SAR calculation. [ABSTRACT FROM AUTHOR]