Vogel-Fulcher Research Articles

Charge transport mechanism, dielectric relaxations and relaxor ferroelectric properties of Sm2MgMnO6 double perovskite

This study investigates the charge transport mechanism, dielectric relaxation and relaxor ferroelectric properties of Sm2MgMnO6 which exhibits monoclinic crystal structure with space group P21/n. The charge carriers conduction mechanism in the temperature range 150 K–239 K and 244 K–304 K are correlated barrier hopping (CBH) and overlapping large polaron tunneling (OLPT), respectively. The maximum barrier height associated to CBH model is 0.26 meV. The dc activation energy associated to CBH and OLPT model are 0.11 eV and 0.91 eV respectively. The polaron hopping energy associated to Mott's variable range hopping model is 0.11 eV at 244 K. The value of tanδ varies from 0.004 to 3.329 in temperature range 151.07 K–306.87 K and frequency range 1 kHz–800 kHz. The temperature variation of ε′, ε″ and tanδ shows a single relaxation which follows Vogel–Fulcher (VF) law. The VF law and the shape of P–E hysteresis loop confirms the relaxor ferroelectric nature of the studied material. The saturated polarization (PMax), remnant polarization (Pr) and coercive field (Ec) depend on both the electric field (E0) and frequency (f). The loop area (A′) and dielectric breakdown field (EBD) depend on E0 as A′∝E02 and EBD∝E0, respectively. The PMax, Pr and Ec depend on f as PMax∝f−0.13, Pr∝f−0.48 and Ec∝f−0.48, respectively. The energy storage efficiency (η) varies with frequency as: η%=20.44f0.21.

Simultaneous enhancement of energy storage performance and thermal stability of NaNbO3-based ceramics via multi-scale modulation

More and more attention is being paid to the environmental friendliness of the dielectric capacitors, which have a rapid charging and discharging speed and steady operation. However, the low recoverable energy storage density (Wrec) limits the practical application of dielectric capacitors in solid-state energy storage devices. In this paper, (1–x) (0.92NaNbO3-0.08Bi(Mg0.5Ti0.5)O3)-xSrTiO3(x = 0.05, 0.10, 0.15, 0.20) energy storage ceramics were fabricated based on various strategies such as nanodomain engineering, component and grain size optimization. Thus excellent energy storage performance (Wrec ∼ 6.0 J/cm3, η ∼ 81.0%) was obtained in NN-BMT-0.15ST. SrTiO3 could enhance the internal disorder, improve the relaxation properties and increase the breakdown field strength of ceramics. Signifi-cantly domain relaxor behavior, as evidenced by Vogel-Fulcher (V-F) model, provides strong evidence for restraining early polarization saturation. In addition, Pulse charge/discharge tests have illustrated that the sample has excellent and stable charge/discharge performance (CD ∼ 1,068.9 A/cm2, PD ∼ 96.1 MW/cm3, t0.9 ≈ 0.99 μs) It is concluded that there is a huge prospect of NN-BMT-0.15ST ceramics as a kind of pulsed-power-storing electronics.

Investigate the effect of the synthesis method on the magnetic dynamic properties of SrAl4Fe8O19 hexaferrite

M-type SrAl4Fe8O19 hexaferrite was synthesized through three different synthesis methods, i.e., solid-state, co-precipitation, and sol–gel auto-combustion, to study the effect of synthesis on the structural and magnetic properties. X-ray diffraction (XRD), Rietveld refinement, high-resolution scanning electron microscope, and SQUID-magnetic property measurement system (MPMS) magnetometer were performed. The structural analysis demonstrated the formation of magnetoplumbite structure by these three synthesis methods. The variation in bond length and bond angle was also observed due to the synthesis methods, which affected the super-exchange interaction of the system. The solid-state method produced larger grains and more significant saturation magnetization i.e., 4.03 µm and 43.16 emu/gm, respectively, than the co-precipitate and sol–gel auto combustion methods. Magnetization–temperature (M−T) measurement revealed that the solid-state synthesized sample showed a higher blocking temperature than the rest. Magnetic susceptibility (χ) was performed with temperature dependence on different frequencies to demonstrate the magnetic dynamic properties of the SrAl4Fe8O19 hexaferrite. AC susceptibility results showed very strong magnetic interaction between particles leading to spin glass action at very low temperatures. The Neel–Arrhenius (N-A) & Vogel-Fulcher (V-F) models were used to determine the jump attempt time (τ0) and E0/KB (energy barrier or activation energy and Boltzmann constant) through AC susceptibility of magnetic particles. The τ0 and E0/KB were observed at about 2.84 × 10-11 sec and 871.31, respectively, for the solid-state synthesized sample by the V-F model.

Enhancement of energy storage and hardness of (Na0.5Bi0.5)0.7Sr0.3TiO3-based relaxor ferroelectrics via introducing Ba(Mg1/3Nb2/3)O3

• Simultaneously achieved high W rec of 5.50 J/cm 3 and η of 90.10% in this system. • Ultrahigh hardness ( H ) of 7.35 GPa is realized in this system. • The improved ESP are explained by first-principles calculation on basis of DFT. • The excellent stability in energy storage has been achieved in this system. High comprehensive performances with large energy storage density ( W rec ), high efficiency ( η ), good hardness ( H ), and large operating temperature range are the main challenge in applications of modern electronics and electrical power systems. Herein, excellent comprehensive energy storage performances [high W rec of 5.50 J/cm 3 , large η of 90.10%, and broad usage temperature range (20–200 °C)] and ultrahigh H of 7.35 GPa in lead-free (Na 0.5 Bi 0.5 ) 0.7 Sr 0.3 TiO 3 -based (BNST) ceramics are achieved synergistically. Improving dielectric breakdown strength ( E b ), mitigating early polarization saturation, large polarization difference, and decreasing grain size are beneficial to the enhancement of comprehensive performances. Further analysis of intrinsic electronic structure indicates that the introduction of Ba(Mg 1/3 Nb 2/3 )O 3 (BMN) is conducive to enhancing E b values of BNST via first-principle calculation upon density functional theory (DFT), which can also be verified by experiments. Significantly domain relaxor behavior, as evidenced by piezoresponse force microscopy (PFM) and Vogel-Fulcher (V-F) model, provides strong evidence for restraining early polarization saturation and large polarization difference. Additionally, for practical applications, the BNST-based ceramics exhibit a large power density (49.26 MW/cm 3 ) and fast discharge time (∼120.00 ns) over broad temperature range (20–140 °C). We believe that these findings in this study can provide an effective guideline approach to attain high-performance capacitors for application in pulsed power capacitors.

Study of canonical spin glass behavior in Co doped LaMnO3

Temperature-dependent magnetic and a.c. susceptibility measurements were done on single phase polycrystalline LaMn1-yCoyO3 (y = 0.1, 0.4) samples. The field cooled and zero field cooled magnetic measurements performed indicate the presence of spin glass state which is established using a.c. susceptibility measurements. The a.c. susceptibility data analyzed using Arrhenius and Vogel–Fulcher (VF) law reveal the presence of canonical spin glass.

Dielectric relaxation and local domain structures of ferroelectric PIMNT and PMNT single crystals

AbstractDielectric relaxation properties of ternary Pb(In1/2Nb1/2)O3‐0.49Pb(Mg1/3Nb2/3)O3‐0.27PbTiO3 (PIMNT27) and binary Pb(Mg1/3Nb2/3)O3‐0.27PbTiO3 (PMNT27) single crystals have been investigated. The dielectric constant peak temperature Tm with frequency obeys the Vogel‐Fulcher (V‐F) law. The dielectric constants at temperatures above Tm can be described by the Lorenz‐type relationship. The fitting parameter δA and ΔTm of PIMNT27 are higher than those of PMNT27, indicating stronger relaxation in ternary PIMNT system. Local nanodomain structures were measured by the piezoelectric force microscopy (PFM). The average autocorrelation function technique was applied to quantify these nanoscale domain patterns. The PIMNT27 exhibits smaller size nanodomains and shorter mean local short‐range correlation length compared to PMNT27. The enhanced local disorder in PIMNT is related to the introduction of In3+ in PMNT system, which can enhance the disorder of B‐site ions. In addition, the evolution of local polarization rotation under a step‐increased tip dc voltage and the mean local short‐range correlation length <ξ> as a function of dc voltage were obtained for both PIMNT27 and PMNT27 single crystals, which are crucial parameters for the understanding of the relationship between dielectric relaxation and local domain structures in relaxor‐PbTiO3 systems.

AC susceptibility and hyperfine interactions of Mg-Ca ions co-substituted BaFe12O19 nanohexaferrites

Magnesium and calcium co-substituted Ba M-type nanohexaferrite (NHFs) is fabricated via sol-gel auto-combustion technique. The phase formation was proved by XRD powder pattern, FESEM and HR-TEM. Magnetic properties of Ba1-2xCaxMgxFe12O19 (x ≤ 0.1) NHFs investigated by Mossbauer Spectroscopy. The variations in line width, quadrupole splitting, isomer shift, the cation distribution of Ca2+ and Mg2+ ions and hyperfine magnetic field values were estimated. The AC magnetic susceptibility and ZFC-FC measurements were also performed for the Ba1-2xCaxMgxFe12O19(x = 0.02 and 0.08) NHFs. The MFC-MZFC results do not show blocking temperature peak, indicating the ferrimagnetic (FM) behavior of prepared products. Different models including Neel-Arhenius (N-A), Vogel-Fulcher (V-F) and critical slowing down (CSD) were tested to evaluate the AC-magnetic susceptibility behaviors. It is demonstrated that the magnetic interactions are important for x = 0.02 NHFs.

Coexistence of cluster ferromagnetism and cluster spin-glass like behaviour in melt-quenched Cu2Mn0.5Fe0.5Al Heusler alloy

We investigated the structural stability and magnetic properties of the melt-quenched Heusler alloy-Cu2Mn0.5Fe0.5Al using X-ray diffraction (XRD), scanning electron microscopy (SEM), dc magnetization and ac susceptibility measurements respectively. The structural analysis by Rietveld refinement showed that the alloy crystallised in L21 structure with no trace of secondary phase in the XRD pattern. The dc magnetic measurements exhibited a thermal irreversibility between field-cooled (FC) and zero field cooled (ZFC) magnetization curves at an irreversible temperature Tirr. A deviation from de Almeida –Thouless like line for Tirrvs. H data was observed, suggesting a possibility of cluster glass (CG) like phase in the sample. To confirm the CG behaviour, frequency dependent ac susceptibility (χac) measurements were carried out on the sample and was analysed by Vogel-Fulcher (VF) and Critical slowing down models. We obtained large relaxation time constants (τ0) from the fit to both the phenomenological models which indicate that the origin of glassy nature may not be from randomly oriented atomic spins like in spin-glasses (SG) but of magnetic clusters. The analysis of nonlinear susceptibilities of the sample confirmed the coexistence of ferromagnetic interactions and glassy nature in the sample. Further confirmation for the glassy nature in the sample was provided by ZFC memory experiments. No anomaly was found corresponding to long-range order in the heat capacity (CP(T)) measurement and a T3/2 dependence was also seen in the electrical resistivity which indicates the magnetic glassiness in the sample.

Cluster spin-glass behavior and memory effect in Cr0.5Fe0.5Ga

We report the structural, static, and dynamic properties of Cr$_{0.5}$Fe$_{0.5}$Ga by means of powder x-ray diffraction, magnetization, heat capacity, magnetic relaxation, and magnetic memory effect measurements. DC magnetization and AC susceptibility studies reveal a spin-glass transition at around $T_{\rm f} \simeq 22$~K. An intermediate value of the relative shift in freezing temperature $\delta T_{\rm f} \simeq 0.017$, obtained from the AC susceptibility data reflects the formation of cluster spin-glass states. The frequency dependence of $T_{\rm f}$ is also analyzed within the framework of dynamic scaling laws. The analysis using power law yields a time constant for a single spin flip $\tau* \simeq 1.1\times10^{-10}$~s and critical exponent $z\nu^{\prime}=4.2\pm0.2$. On the other hand, the Vogel-Fulcher (VF) law yields the time constant for a single spin flip $\tau_0 \simeq 6.6\times10^{-9}$~s, VF temperature $T_{\rm 0}=21.1\pm0.1$~K, and an activation energy $E_{\rm a}/k_{\rm B} \simeq 16$~K. The value of $\tau*$ and $\tau_0$ along with a non-zero value of $T_{\rm 0}$ provide further evidence for the cluster spin-glass behaviour. The magnetic field dependent $T_{\rm f}$ follows the de Almeida-Thouless line with a non-mean-field type instability, reflecting either a different universality class or strong anisotropy in the spin system. A detailed non-equilibrium dynamics study via relaxation and memory effect experiments demonstrates striking memory effects. All the above observations render a cluster spin-glass behaviour which is triggered by magnetic frustration due to competing antiferromagnetic and ferromagnetic interactions and magnetic site disorder. Moreover, the asymmetric response of magnetic relaxation with respect to the change in temperature, below $T_{\rm f}$ can be explained by the hierarchical model.

Study of dynamic behaviors for nano Fe-doped MgB2 superconductor via ac-susceptibility measurements

Nano-sized superconducting polycrystalline particles of Mg1-xFexB2 (0.00 ≤ x ≤ 0.04; space group P6/mmm) were synthesized through the solid state reaction route. The effect of nano-Fe substitution on ac-susceptibility at varying frequency range from 1 to 3 kHz in addition with ac-amplitude (Hac) and dc-applied field (Hdc) were explored. The dynamical behavior of nano-particles shows the strong magnetic interaction between the nano-clusters with the increase of doping content. This is due to the successful inclusion of Fe3+ ions in the matrix of MgB2. X-ray powder diffraction (XRD) reveals the reduction of average grain size with increasing the doping level. Neel-Arrhenius (N-A) and Vogel-Fulcher (V-F) models were discussed to distinguish the dynamical behaviors of the nano-particles. Remarkably, the V-F model elucidates the experimental results much better than N-A model with the support of some parameters like jump attempt frequency, activation energy, magnetic anisotropy constant and V-F temperature.

Synthesis, structure, dielectric properties and relaxor behavior of a novel solid solution (1-x)Pb(Mg1/3Nb2/3)O3-xBi(Zn2/3Nb1/3)O3

A solid solution of (1-x) Pb(Mg1/3Nb2/3)O3-xBi(Zn2/3Nb1/3)O3 [(1-x)PMN-xBZN)] has been prepared in the form of ceramics with x = 0-0.20 by solid state reaction method. The crystal structure and dielectric properties are investigated. An enhanced relaxor behavior is found when incorporating BZN into canonical relaxor PMN due to the increased chemical disorder. The high temperature slope of dielectric constant as a function of temperature is consistent with the empirical quadratic law. The frequency dependence of the temperature of the dielectric maximum follows the Vogel-Fulcher (V-F) law.

Structural, electrical and relaxor properties of Sc-In solid solution in tetragonal tungsten bronze ceramics

The electrical properties of a family of tetragonal tungsten bronze (TTB) materials, Ba6Sc1-xInxNb9O30 (x = 0.25, 0.5, 0.75), which display relaxor properties were characterised using high- and low-temperature dielectric spectroscopy. All powders were synthesised at 1250 °C (24 h) + 1350 °C (6.5 h), while the pellets were further sintered at 1350 °C (12 h). At high temperature, the electrical conductivity in all samples is dominated by a single response, attributed to the bulk response, while the subtle asymmetry of the imaginary impedance peak suggests a minor contribution of the grain boundary response. In general, the Sc-In solid solutions samples exhibit similar electrical behaviour to the Sc compound, x = 1 reported previously (Ceram. Int. 2016, 42, 11810–11821). At low temperature all compounds exhibit frequency dependent relaxor behaviour. With increasing the content of In, the dielectric peaks are more asymmetric and the curves flatten more at temperatures above the transition temperature. The dipole freezing temperature, TVF, determined by Vogel-Fulcher (VF) analysis does not simply increase linearly as a function of M3+ (Sc3+,In3+) cation size, the extrapolation of VF-like curves results in considerably different values when compared to those found previously, since the acquired dielectric data are very sensitive to preparative conditions.

Glass Transition and Dynamics of the Polymer and Water in the Poly(vinylpyrrolidone)-Water Mixtures Studied by Dielectric Relaxation Spectroscopy.

In this study, broadband dielectric spectroscopy and differential scanning calorimetry (DSC) measurements are performed to study the dynamics of water and polymers in an aqueous solution of poly(vinylpyrrolidone) (PVP) with concentrations of 60, 65, and 70 wt % PVP in a temperature range of 123-298 K. Two distinct relaxation processes, l- and h-processes, which originate from the segmental chain motion of PVP and the primary relaxation process of water, respectively, are observed simultaneously. The relationship between l- and h-processes and their temperature dependences mimic those of the α-process and Johari-Goldstein β-process, which are observed in ordinal glass formers. The relaxation time of the l-process, τl, obeys the Vogel-Fulcher (VF)-type temperature dependence, and the glass-transition temperature of the l-process, Tg,l, which is defined by the temperature that is reached in a τl of 100-1000 s, shows good agreement with the calorimetric Tg obtained by DSC. The temperature dependence of the relaxation time of the h-process, τh, exhibits a crossover from VF to Arrhenius behavior at the so-called fragile-to-strong transition (FST) of water at Tg,l. The temperature dependence of the relaxation strength of the h-process, Δεh, increases with a decrease in temperature from 298 K to Tg,l. Below Tg,l, Δεh is nearly constant or slightly decreases with decreasing temperature. According to previous studies on aqueous solutions of sugars and alcohols, the Δε of the ν-process, which originates from local motion of water, decreases with decreasing temperature above the Tg of the α-process, which originates from the cooperative motion of the solute and water. Therefore, the l-process in the PVP-water mixture is not a result of the cooperative motion of PVP and water but rather a result of the polymer-polymer cooperative motion of PVP. In addition, agreement among Tg,l, the temperature of the FST of water, and calorimetric Tg suggests that the FST of water occurs at Tg.

Novel optically active lead-free relaxor ferroelectric (Ba0.6Bi0.2Li0.2)TiO3

We discovered a near-room-temperature lead-free relaxor-ferroelectric (Ba0.6Bi0.2Li0.2)TiO3 (BBLT) having A-site compositionally disordered ABO3 perovskite structure. Microstructure-property relations revealed that the chemical inhomogeneities and development of local polar nano-regions (PNRs) are responsible for dielectric dispersion as a function of probe frequencies and temperatures. Rietveld analysis indicates mixed crystal structure with 80% tetragonal structure (space group P4mm) and 20% orthorhombic structure (space group Amm2), which is confirmed by the high resolution transmission electron diffraction (HRTEM). Dielectric constant and tangent loss dispersion with and without illumination of light obey nonlinear Vogel–Fulcher (VF) relations. The material shows slim polarization–hysteresis (P–E) loops and excellent displacement coefficients (d33 ~ 233 pm V−1) near room temperature, which gradually diminish near the maximum dielectric dispersion temperature (Tm). The underlying physics for light-sensitive dielectric dispersion was probed by x-ray photon spectroscopy (XPS), which strongly suggests that mixed valence of bismuth ions, especially Bi5+ ions, comprise most of the optically active centers. Ultraviolet photoemission measurements showed most of the Ti ions are in 4 + states and sit at the centers of the TiO6 octahedra; along with asymmetric hybridization between O 2p and Bi 6s orbitals, this appears to be the main driving force for net polarization. This BBLT material may open a new path for environmental friendly lead-free relaxor-ferroelectric research.

Vogel–Fulcher analysis of relaxor dielectrics with the tetragonal tungsten bronze structure: Ba6MNb9O30 (M = Ga, Sc, In)

In-depth analysis of the relaxor behaviour of Ba6MNb9O30 (M = Ga, Sc, In) tetragonal tungsten bronze (TTB) ceramics was carried out. Powder X-ray diffraction and scanning electron microscopy were performed in order to confirm the formation of desired phases and to determine the microstructure. Low-temperature dielectric spectroscopy was used in order to characterise the dielectric properties of these materials; the degree of relaxor behaviour was investigated in relation with the increase of ionic radius of the M cation on the B-site of the TTB structure. The dynamics of dielectric relaxation of dipoles was studied by fitting the dielectric permittivity data to the Vogel–Fulcher (VF) model in order to monitor the reproducibility and validity of the physical results. Restrictions to the VF fit were attempted besides the regular “free-fit” by constraining some of the fundamental relaxation parameters to physically sensible values. We show that VF fits are very sensitive to the fitting range resulting in a large range of fundamental parameters for the dielectric relaxation processes, and that the restriction of the frequency domain due to experimental noise or instrumentation limits has a dramatic influence on the values obtained.

Glassy behavior study of dysprosium doped barium zirconium titanate relaxor ferroelectric

We report the glassy behavior of dysprosium doped barium zirconium titanate single phase perovskite ceramics with general formula Ba1−xDy2x/3Zr0.25Ti0.75O3 prepared by solid-state reaction method. Temperature and frequency dependent dielectric studies of the ceramics reveal relaxor behavior. A non-Debye relaxation, which is analogous to the magnetic relaxation in spin-glass system, is observed clearly around temperature of dielectric permittivity maximum (Tm). Frequency dependence of Tm governed by production of polar nano-regions is analyzed using Debye relation, Vogel-Fulcher (V-F) relation and power law. A clear change in dynamic behavior is observed by power parameter which is related to growth of interactions between polar nano-regions with different composition. Various parameters like activation energy for relaxation, freezing temperature, relaxation frequency, etc., are determined after non-linear curve fitting. Temperature dependence of dielectric constant at temperatures much higher and lower than Tm is analyzed by two exponential functions, which gives an idea about the production of polar clusters at high temperature and distribution of freezing temperatures at lower temperature. Various other associated parameters are calculated by non-linear curve fitting and their significance has been explained.

Freezing in relaxor ferroelectrics and dipolar glasses

A recently proposed semi-phenomenological model of freezing in relaxor ferroelectrics, based on the concept of polar nanoregions (PNRs) embedded in a polarizable medium, is reviewed. A generalized Landau-type free energy for the medium is discussed, where the medium polarization couples linearly to the PNR polarization. When the fourth-order Landau coefficient is negative (b < 0), the correlation radius rc, which measures the PNR size, depends on the temperature T and the applied field E. As T is lowered or E increased, rc increases and the volume of a cluster of PNRs grows until the percolation limit is reached. This leads to a generalized expression for the Vogel-Fulcher (VF) relaxation time with a field-dependent VF freezing temperature T0(E). The case b > 0, in which the percolation mechanism cannot be realized, is considered to be appropriate for dipolar glasses.

Comparative study of phase structure and dielectric properties for K0.5Bi0.5TiO3BiAlO3 and LaAlO3BiAlO3

In this work, two perovskite‐type compounds, K0.5Bi0.5TiO3 and LaAlO3, have been selected as host material to incorporate with BiAlO3 using a solid‐state reaction route. The phase evolution and dielectric properties for both systems have been investigated in detail. For the K0.5Bi0.5TiO3BiAlO3 system, it is interesting to find that when using Bi2O3, Al2O3, K2CO3, and TiO2 as starting materials, the formed compounds are K0.5Bi0.5TiO3K0.5Bi4.5Ti4O15 and Al2O3 only plays a dopant role. There are two distinct dielectric peaks appearing in the patterns of temperature dependence of dielectric constant, corresponding to the phase‐transition points of perovskite‐type K0.5Bi0.5TiO3 and Aurivillius‐type K0.5Bi4.5Ti4O15, independently. In comparison, using Bi2O3, Al2O3, and La2O3 as starting materials, the pure perovskite phase LaAlO3BiAlO3 can be obtained. Compared to the inherent paraelectric behavior in LaAlO3, the diffuse phase‐transition phenomena can be observed in the LaAlO3BiAlO3 binary system, which corresponds well to the Vogel–Fulcher (VF) relationship. Moreover, compared to pure LaAlO3, the synthesized LaAlO3BiAlO3 compound shows enhanced dielectric properties, which are promising in application as gate dielectric materials.

Relaxor ferroelectric behavior ofBaBi4Ti4O15aurivillius ceramic

Aurivillius type compound BaBi4Ti4O15(BBT) ceramic was prepared by solid state reaction route and its electrical properties were studied. X-ray diffraction (XRD) pattern showed orthorhombic structure with space group A21am confirming it to be an m = 4 member of the Aurivillius oxide. The scanning electron microscope of the sintered pellet showed a plate-like morphology of grains which is a characteristic feature of the Aurivillius compounds. The temperature and frequency dependence dielectric study showed a shifting of transition temperature with frequency indicating relaxor type behavior in the material. The diffuseness parameter (γ) established the relaxor nature and it was attributed to the A-site cationic disorder. The dielectric relaxation obeyed the Vogel–Fulcher (VF) relation and various parameters like activation energy for relaxation, freezing temperature, relaxation frequency were determined after nonlinear curve fitting. The temperature dependence of dielectric constant at temperatures much higher and lower than Tmwas analyzed by two exponential functions, which gives an idea about the production of polar clusters at high temperature and the distribution of freezing temperatures at lower temperature. Various other associated parameters were calculated by nonlinear curve fitting and their significance has been explained.

Magnetoelectric coupling and relaxor ferroelectric properties of Pb 0.7Sr 0.3(Fe 0.012Ti 0.988)O 3 thin film

We present the electric and magnetic properties of nanostructured Pb 0.7 Sr 0.3 (Fe 0.012 Ti 0.988 )O 3 (PSFT3) thin film. The magnetoelectric coupling has been studied by polarization hysteresis loops under the influence of an applied magnetic field and a phase transition anomaly. At room temperature PSFT3 film shows diffuse phase transition of dielectric diffusivity ( γ = 1.94). The Vogel–Fulcher (VF) relation implies the relaxor characteristics of the film by extracting the VF freezing temperature and the activation energy of polar nanoregions.