Temperature Dependence Of Frequency Research Articles

Phase transition investigation of ferroelectric and dielectric properties of (NH 2 CH 2 COOH)3 H2SO4 crystal using green function method and two sublattice PLCM model Hamiltonian

The Greens function technique and extended two sublattice pseudospin lattice coupled-mode (PLCM) model Hamiltonian have been applied to study the phase transition mechanism in (NH2CH2COOH)3H2SO4 compound. The two sublattice PLCM model Hamiltonian is modified by considering anharmonic phonon interactions, extra spin-lattice interactions, and an external applied electric field term. By using the double-time thermal-dependent Green function technique, the theoretical equations for the total shift, total width, normal mode frequency, transition temperature, relative permittivity, dielectric tangent loss, acoustic attenuation and spontaneous polarization are derived. By fitting the distinct model parameters in the theoretical equations, we calculated the temperature dependence of normal mode frequency, relative permittivity, tangent loss, acoustic attenuation and spontaneous polarization. The numerically obtained results are hold well and correlated with experimental data.

Influence of acoustic modes on resonance properties of a quartz tuning fork immersed in superfluid 4He and liquid mixtures 3He–4He

The oscillating quartz tuning fork method has been used to study resonance phenomena in experimental cells of different sizes filled with superfluid 4He and concentrated liquid mixtures of 3He–4He. An analysis of the temperature dependence of the resonance frequencies of the tuning forks showed that in a number of cases, the incompressible fluid model is not sufficient to interpret the experimental results and that acoustic processes in the cell should be taken into account. The frequencies of the resonances of the first sound in cylindrical geometry are estimated and their influence on the resonant frequencies of the tuning fork is shown, which can lead to a distortion of the shape of the resonant line. A comparison is made between experimental results for superfluid 4He and mixtures of 3He-4He with light isotope concentrations of 5% and 15%. It is shown that, in contrast to pure helium, the model of a viscous incompressible fluid cannot be applied to mixtures, even in the absence of first acoustic resonances. This can be explained by the fact that, when studying concentrated solutions, the excitation of the second sound along with the first can have a noticeable effect on the resonance characteristics of the tuning fork.

Understanding spin-dependent vibrational frequencies in Fe(II) metal organic coordination complexes

We investigated the compositional and temperature (T) dependences of vibrational frequencies in Hofmann-type Fe(L)2[M(CN)4] spin-crossover (SCO) coordination polymers in which {M = Ni, Pd or Pt with L = pyridine (py)}, or {L = 3-Cl-py or 3-methylpy with M = Ni}, using Raman spectroscopy. The SCO-driven peak shifts (in wavenumber) ranged up to ∼170 cm−1, manifesting significant spin-dependent structural evolutions. Furthermore, there appear clear HS signatures even at T ≪ TSCO for L = 3-Cl-py or 3-methylpy implying the steric effects of the organic ligands on the HS trapping. Meanwhile, for L = py, such HS trapping at the low temperature was not significant although some spectra taken under high laser fluence exhibit light-induced excited spin state trapping (LIESST) effect. The mechanism of the LIESST is discussed in detail in terms of the M d – C 2sp hybridization effects.

Temperature dependence of spatial nanoheterogeneities of shear modulus in supercooled glycerol.

The boson peak in the terahertz vibrational spectrum carries information about nano-heterogeneities in the shear modulus in glass formers. Its evolution upon heating or cooling in a supercooled liquid state may shed light on the temperature dependence of heterogeneities. For this purpose, an analysis of the light scattering spectra of supercooled glycerol in the spectral range of the boson peak and fast relaxation was carried out and the parameters of the boson peak in the temperature range 180-330K were determined. The temperature dependent frequency of the boson peak was then expressed in terms of the mean-square amplitude of the shear modulus fluctuations. This was done using the heterogeneous elasticity theory in combination with the perturbation theory on small fluctuations and Ioffe-Regel criterion for transverse vibrations in glass formers. The contribution of structural relaxation effects to phonon damping becomes significant with increasing temperature. It is shown here that structural relaxation largely determines the temperature dependence of the mean-square fluctuations of the shear modulus at high temperatures. By solving the inverse problem, the temperature dependence of shear modulus fluctuations was obtained. It shows a rapid decrease above ∼250K with a linear extrapolation going to zero at the so-called Arrhenius temperature TA = 350K. Comparison with literature data on the Landau-Placzek ratio shows that they have a similar temperature dependence at T < TA, which is explained by the appearance of nanometer scale spatial heterogeneities below TA. This is confirmed by the temperature dependence of the amplitude of the boson peak.

Electron–phonon coupling and a resonant-like optical observation of a band inversion in topological crystal insulator Pb1−x Sn x Se

The optical reflectivity of n-type Pb0.865Sn0.135Se and Pb0.75Sn0.25Se solid solutions was measured in the THz spectral region energetically corresponding to optical phonon excitations and in the temperature range from 40 K to 280 K. The first solid solution exhibits an open energy gap with trivial band ordering at all temperatures, while for the second one the transition from trivial insulator to topological crystal insulator phase is expected. The analysis of Pb0.75Sn0.25Se data performed within the dynamic dielectric function formalism revealed an anomaly of resonance-like character in the temperature dependence of LO phonon frequency. The formula for LO phonon energy renormalization reproduced observed anomaly for energy gap equal to zero, the phase transition occurred at T 0 = (172 ± 2) K. This effect was absent for Pb0.865Sn0.135Se. Present results show that reflectivity measurements in the THz range in the vicinity of LO phonon frequency can be valuable experimental method for precise determining of band inversion temperature in narrow-gap topological materials.

Effect of rare earth (Ho and Er) co-substitution on the magnetic and dielectric properties of nanocrystalline cobalt ferrites

Nanocrystalline cobalt ferrites co-substituted with rare earth Ho and Er (CoFe2-2xHoxErxO4, 0 ≤x≤0.10) have been synthesized via the sol-gel method. X-ray Diffraction (XRD) confirmed the single-phase spinel structure with reduced crystallite sizes (65 nm–12 nm), micro-strain (ε) and increased lattice constant (a) with Ho–Er co-substitution. Rietveld refinement and theoretical computation revealed Ho and Er occupancy at octahedral sites and Fe and Co ions redistribution between the tetrahedral and octahedral sites. Infrared spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS) supported the formation of the desired spinel structure, aggregated spherical morphology, chemical stoichiometry and elemental states. Magnetic measurements showed a systematic decrease in saturation magnetization (Ms), magnetocrystalline anisotropy (K1), coercivity (Hc) and Curie temperature (Tc) with Ho–Er co-substitution. Electron Spin Resonance (ESR) exhibited asymmetric resonance peaks, reduced resonance field (Hr), linewidth (ΔHpp) and deviation in Lande g values. Impedance spectroscopy revealed two conduction mechanisms (holes and electrons) with distinct activation energies (EaI and EaII). Modulus spectrum analysis confirmed the thermally activated sample-electrode effects and the Nyquist plots indicated the dominant contribution of the grain boundary resistance to the conduction process. A notable enhancement in the dielectric constant (ε′) was observed with Ho–Er co-substitution. The ac conductivity (σac) followed the Jonscher Power Law (JPL). The temperature-dependent frequency exponent s(T), suggests the existence of two conduction mechanisms: non-overlapping small polaron tunneling (NSPT) and correlated barrier hopping (CBH).

Electrical properties and conduction mechanisms of Ba0.75Sr0.25Ti1-xZrxO3 ceramics synthesized by sol-gel route

A series of Ba0.75Sr0.25Ti1-xZrxO3 (x = 0, 0.01, 0.03, 0.05, and 0.1) ceramics were synthesized via a facile sol-gel route. The confirmation of a tetragonal structure was achieved through Rietveld refinement of the powder X-ray diffraction (XRD), and the finding was subsequently corroborated by Raman spectroscopy. The Scanning electron microscopy (SEM) confirmed the roughly cubical-shaped grains and average grain size is 0.31 μm for x = 0 and 0.70 μm for x = 0.05. The electrical properties such as dielectric constant, dielectric loss and ac/dc conductivity were investigated as a function of temperature and frequency. The Jonscher's universal power law (JPL) and Arrhenius equation have been used for the analysis of conductivity. The electrical conductivity variation at intermediate frequencies was explained using JPL. The Super-linear power law (SPL) explains the electrical response at higher frequencies. The temperature-dependent frequency exponents ‘s1’ and ‘s2’ were employed to predict the quantum mechanical tunneling (QMT), non-overlapping small polarons hopping (NSPT), and correlated barrier hopping (CBH) conduction mechanisms.

PARAMETERS OF THE PERTURBED STATE OF THE DENDRITE TIP IN DEEPLY SUPERCOOLED NICKEL AND COPPER MELTS

The object of study is the morphological stability of the tip of a free dendrite in a supercooled melt of a pure substance. Areas of deep supercooling are considered: for nickel DT &gt; 166 K, for copper – DT &gt; 180 K. A distinctive feature of the processes being studied is the presence of two propagation velocities of small disturbances (velocities of “sound”). The dependences of these rates on the supercooling of the melt were determined. The periodic and coordinate-aperiodic modes of perturbation of the growth line have been studied in detail. For these stable regimes, the possibility of observing the same speed of the disturbance wave in two processes, differing from each other in the size of the spatial inhomogeneity of the background in front of the wave and the characteristic wave attenuation times, was discovered. It is shown that aperiodic instability appears if, after the passage of the wave front, the width of the growth line inhomogeneity zone decreases. The resonant excitation mode of the dendrite tip demonstrates important differences between the properties of the nickel and copper melts. First of all, this relates to the temperature dependences of the resonant frequency and the speed of a standing wave formed in the vicinity of the vertex. Numerical calculations are presented and graphic information is presented illustrating the patterns of growth of nickel and copper dendrites.

Structural and ionic conduction study of Sm–Pr co-doped ceria electrolyte materials for LT-SOFC applications

Samarium praseodymium (Sm–Pr) co-doped ceria was synthesized by the co-precipitation technique as an electrolyte for low-temperature solid oxide fuel cell (LT-SOFC) applications. The structural, morphological, compositional, and electrical characterization of the synthesized samples were evaluated via x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX) and impedance spectroscopy. The generation of a single-phase fluorite structure of co-doped ceria without any secondary phases has been verified by XRD analysis, exhibiting the successful incorporation of Sm and Pr ions into the ceria lattice. Vegard's law is utilized for Pr redox behavior explaining the variation in lattice constant values. SEM pictures show that the co-doped ceria powder has a homogeneous and well-dispersed microstructure, and has enhanced particle size. The impedance spectroscopy results indicate that Sm–Pr co-doped ceria has much higher ionic conductivity than single-doped ceria. The highest amount of ionic conductivity (σionic) for the composition Ce0.80Sm0.10Pr0.10O2−δ recorded as 2.12×10−2S/cm at 500°C, and 6.19×10−2S/cm at 750°C with the lowest activation energy Ea=0.48eV, which has been not reported earlier. Sm and Pr are chosen as dopants because of their capacity to generate oxygen vacancies and improve ceria's ionic conductivity. This study contributes to the enhancement in the ionic conductivity of co-doped ceria by co-precipitation technique and the temperature-dependent frequency exponent factor "s" is also explored to comprehend the conduction mechanism of the prepared samples.

Summerfield scaling model and conduction processes for the determination of the transport properties of the Ba0.25Sr0.25Fe2.5O4 ceramic

The conductivity spectra of the iron oxide Ba0.25Sr0.25Fe2.5O4 revealed that sample exhibits a semi-conductor behavior within the temperature and frequency. Based on the direct current analysis, charge carrier transport was assisted by a disorder energy below θD/4. For θD/4≤T≤θD/2, electrical conductivity was attributed to the contribution of the Mott-VRH mechanism. However, for T≥θD/2, conduction phenomena were supported by the thermal activation of the small polaron hopping mechanism.At higher frequencies, the electrical characteristics of our sample were clarified through the application of a superlinear power law.The contributions of different conduction processes were predicted using temperature dependent frequency exponents.The hopping energy was found to decrease as the frequency increased, a trend that can be linked to variations in the polaron radius. The impedance results validate the involvement of the resistive grain boundary in the electrical properties and indicate the presence of multiple electrical relaxation phenomena in the Ba0.25Sr0.25Fe2.5O4 sample.

The temperature dependence investigation of the frequency dispersion of the electrical properties of lithium-iron spinel doped with La, Y

The temperature-frequency dependences of the electrical characteristics of Li2 Fe2,5-x Mex O4 (Ме=La;Y, x=0.01; 0.03; 0.05) spinels synthesized by the «sol-gel» autocombustion technology were obtained by the method of impedance spectroscopy in the temperature range of 298-473 K.&#x0D; Based on their analysis, the main mechanisms of conductivity of these materials in the studied temperature range were identified: hopping and activation, which are competing. The effect of doping lithium-iron spinels with rare-earth metal impurities on these conductivity mechanisms has been investigated. It has been established that the presence of impurities in small concentrations in the synthesized samples significantly decreases their conductivity, mainly due to destruction of the hopping mechanism of electronic conductivity.

Large magnetocaloric effect and exchange bias properties in Mn-Ni-Co-Sn full Heusler alloy

We have studied the structural, magnetic, magnetocaloric properties and exchange bias (EB) of a Mn-rich Mn-Ni-Co-Sn Heusler alloy, by means of the combined experimental and theoretical investigations. The alloy possesses tetragonal structure at room temperature (RT), and exhibits a first order martensitic transition at around 335 K. It also shows a large magnetocaloric effect in the vicinity of martensitic transition, with a maximum isothermal magnetic entropy change of around 35 J/kg.K, which is significantly larger than that reported for many other Heusler systems. Frequency dependence of spin freezing temperature obeying the dynamical scaling and Vogel-Fulcher law, along with the memory effect confirms the presence of cluster spin glass (CSG) state at low temperatures in the alloy. It shows EB effect at low temperatures, with a maximum EB field of 0.099 Tesla at 2 K, after field cooling in presence of 1 Tesla. Strong exchange coupling among the CSG clusters embedded in a strong ferrimagnetic matrix is found to be responsible for the observed EB. Ab-initio calculations using density functional theory on a representative Mn50Ni35.94Co6.25Sn7.81 alloy (very close to our experimental composition) shows the tetragonal structure with the ferrimagnetic ordering as the ground state, which is in good agreement with the experimental results. Exchange mechanism behind the observed EB in the present alloy has been discussed in the light of varying interatomic distances between different atomic pairs, and hence the magnetic coupling.

Experimental Analysis of Rayleigh and Sezawa Modes Resonance Frequencies in SAW Devices Manufactured on Sc0.3Al0.7N/Si†

GHz operating single port SAW resonators have been manufactured on Sc0.3Al0.7N/Si substrate. The thickness of the ScAlN thin layer was 0.8 μm. Advanced nano‐lithographic techniques have been developed for devices manufacturing. Rayleigh and Sezawa modes have been evidenced on Sc0.3Al0.7N/Si structure. The targeted applications are temperature sensors for harsh environmental operations. The sensitivity and temperature coefficient of frequency (TCF) of the manufactured devices have been experimentally determined and analyzed. The mode shapes of the resonances that appear in the devices supported on Sc0.3Al0.7N/Si substrate were evidenced by finite element method (FEM) simulations. A technique that combines FEM with Coupling of Modes (COM) was used for the determination of the resonance frequencies. Simulations performed for the temperature dependence of the resonance frequency led to results close to the experimental ones for the Rayleigh mode as well as for the Sezawa mode for devices supported on Sc0.3Al0.7N/Si substrate. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Upward vibrational frequency shift due to electron–phonon polar-coupling interaction in C12H17ClN4OS·HCl·H2O crystals

Electron–phonon (e–p) polar-coupling interactions in C12H17ClN4OS·HCl·H2O crystals exhibiting an upward frequency shift with increasing temperature are investigated using terahertz and far-infrared spectroscopies, and the structural condition required for effective e–p polar-coupling interactions in crystals are uncovered. X-ray crystallography and first-principles calculations reveal that the key structure for the e−p polar-coupling interaction is an open cavity near the considered vibration. Based on the temperature-dependent frequency shift proportional to the Bose−Einstein statistical factor, the interaction strength and characteristic frequency of phonons interacting with electrons are determined at 5.3 × 10–3 cm–1 K–1 and 76.6 cm–1, respectively. From the phonon dispersion curves exhibiting LO (longitudinal optical)–TO (transverse optical) splitting, we find that the highest frequency LO phonon participates in the polar-coupling interaction.

Research on Changes in the Phase Shift Angle and Admittance of the Cellulose–Bio-Oil Composite under the Influence of Increasing Moisture during the Long-Term Operation of Power Transformers

In this study, the temperature–frequency dependencies of the pressboard–bio-oil–water nanoparticle composite’s fundamental parameters—phase shift angle and admittance—were examined using the Frequency Domain Spectroscopy method. Measurements were conducted in a frequency range of 10−4 Hz to 5 × 103 Hz at temperatures ranging from 293.15 K to 343.15 K, with a step of 10 K. The temperature stabilization accuracy was less than ±0.05 K. A total of 15 Arrhenius plots were determined for various phase shift angle values, from which 15 values and the average activation energy of relaxation time were determined. Similarly, the values of the activation energy of admittance relaxation time and the activation energy of admittance were determined. It was established that all three average values are identical within the bounds of uncertainty. Based on 45 values, a generalized activation energy was determined, with a value of ΔW ≈ (1.032 ± 0.0196) eV. Using the generalized activation energy value, the phase shift angle curves determined for all temperatures were recalculated to a temperature of 293.15 K. It was found that after conversion, all curves perfectly overlap. A similar operation was carried out for the frequency dependencies of admittance. In this case, too, the recalculated dependencies perfectly match. This means that the shape of the frequency dependencies of the phase shift angle and admittance depends solely on the moisture content in the pressboard–bio-oil–water nanodrop composite. The position of the curves in doubly logarithmic coordinates depends only on temperature and is determined by the generalized activation energy Using the generalized activation energy determined in this study will allow for the development of accurate methods for estimating moisture content in cellulose insulation of power transformers containing bio-oil. This will contribute to the detection of critical moisture content, which is about 5% by weight, and to the elimination of the risk, associated with such a high moisture content, of catastrophic failure of power transformers.

Temperature dependence of growth-sector-dependent Raman spectra of boron-doped diamonds synthesized at high-pressure high-temperature

Single crystals of boron-doped diamond (BDD) were synthesized by the temperature gradient method in high-pressure and high-temperature conditions in the Fe–Al–B–C system, and multisectoral diamond plates were extracted. Temperature-dependent (77–600 K) high-resolution Raman spectroscopic studies have been carried out to investigate the behavior of anharmonic phonon decay in the {001}, {113}, and {111} growth sectors of multisectoral diamond plates with different content of boron impurities (⩽80 ppm) and compare with the data for undoped IIa diamond. Micro-Fourier transform infrared spectroscopy was used to estimate the spatial distribution of uncompensated boron impurity [Na-Nd] in BDD plates by analyzing boron-related absorption peaks. The plates were shown to have non-uniform growth-sector-dependent content of uncompensated boron impurity in the range from 1.1 × 1018 to 1.4 × 1019 cm−3. The effects of anharmonic decay (damping) of optical phonons in BDD are studied by modeling the temperature dependence of phonon frequency and linewidth of the diamond’s F2g and boron-induced vibrational modes. The extrapolated zero-temperature optical phonon linewidth and frequency and the anharmonic nature of their linear relationship are determined as a function of the growth sector and boron doping. The predominant mechanisms and parameters of the anharmonic decay of optical phonons are determined, which is of fundamental importance for the thermal conductivity of semiconductor materials. The anharmonic phonon decay remained the predominant process at higher temperatures, irrespective of the doping level.

Temperature sensitive contact modes allosterically gate TRPV3.

TRPV Ion channels are sophisticated molecular sensors designed to respond to distinct temperature thresholds. The recent surge in cryo-EM structures has provided numerous insights into the structural rearrangements accompanying their opening and closing; however, the molecular mechanisms by which TRPV channels establish precise and robust temperature sensing remain elusive. In this work we employ molecular simulations, multi-ensemble contact analysis, graph theory, and machine learning techniques to reveal the temperature-sensitive residue-residue interactions driving allostery in TRPV3. We find that groups of residues exhibiting similar temperature-dependent contact frequency profiles cluster at specific regions of the channel. The dominant mode clusters on the ankyrin repeat domain and displays a linear melting trend while others display non-linear trends. These modes describe the residue-level temperature response patterns that underlie the channel's functional dynamics. With network analysis, we find that the community structure of the channel changes with temperature. And that a network of high centrality contacts connects distant regions of the protomer to the gate, serving as a means for the temperature-sensitive contact modes to allosterically regulate channel gating. Using a random forest model, we show that the contact states of specific temperature-sensitive modes are indeed predictive of the channel gate's state. Supporting the physical validity of these modes and networks are several residues identified with our analyses that are reported in literature to be functionally critical. Our results offer high resolution insight into thermo-TRP channel function and demonstrate the utility of temperature-sensitive contact analysis.

Structural, electrical and dielectric properties of ZnFe2O4/Cu2S 3D heterostructures

This work reports the fabrication of zinc ferrite-copper sulphide (ZnFe2O4/Cu2S) 3D heterostructures and subsequent investigation of the spectroscopic behaviour of various electrical parameters like conductivity, impedance and dielectric loss. The study reveals a non-monotonic behaviour of the real component of impedance (Z’), while the imaginary component of impedance (Z’) exhibits a temperature-dependent relaxation frequency, with an estimated activation energy (E a ) of 220.13 meV. The dc conductivity (σ dc ) measurements reveal the semiconducting nature of the sample and a transition from a ferrimagnetic to a paramagnetic behaviour is reported at the Curie temperature of 327 K. In case of ac conductivity (σ ac ), Jonscher’s power law σ ac = Aω n is followed and the exponent n is found to lie in the range 0.679–0.735 at different temperatures, which is best fitted into a polynomial of degree six. The temperature variation of n is suggestive of the overlapping large polaron tunnelling (OLPT) model. Further, ac activation energy (E ac ) is also calculated, which is found to be smaller than the dc activation energy (E dc ), indicating electron hopping between Fe3+ and Fe2+ ions. The numerically computed staying time (τ) of electrons in Fe3+/Fe2+ ionic sites varies with frequency as well as with temperature, ranging from 10−6s to 10−19s. A significant decrease in dielectric loss (tanδ) to the tune of 99% (from 75 at ∼100 Hz to 0.89 at ∼1 MHz) is reported at room temperature. In the present scenario, when smart materials like spinel ferrites have garnered significant attention for their promising magnetic and electric properties, our studies of the ZnFe2O4/Cu2S 3D heterostructures may provide immense possibilities for tailored applications in various electromagnetic applications.

Role of structural, morphological, and electronic characteristics in investigating the low temperature transport and magnetic behavior of Sr doped Sm2NiMnO6

Oxide double perovskites of the form R2NiMnO6 (R= rare-earth) are known to possess the multifunctional behavior. Herein, we have induced structural and electronic modifications in Sm2NiMnO6 system by Sr doping to form Sm2−xSrxNiMnO6 (x = 0.0, 0.2, and 0.4) and accordingly investigated the structural, morphological, electronic, dielectric, magnetic and magnetoresistance properties. Sm2NiMnO6 has monoclinic structure with P21/n space group and doping with Sr does not change the phase of compound. Microstructure studies suggest a decrease in the grain size with increase in Sr doping while elemental overlay and analysis suggest the presence of known elements in uniformity. Chemical valency indicates the existence of mixed valence of Ni and Mn cations along with presence of oxygen vacancies in all the sample of Sm2−xSrxNiMnO6 (x = 0.0, 0.2, and 0.4). Frequency (200 Hz to 2 MHz) and low temperature (100–320 K) dependence of dielectric measurements have been carried out to observe the behavior of dielectric constant and dielectric loss. With increase in concentration of Sr, the dielectric constant decreases while the dielectric loss increases. Temperature variation of ac conductivity as well as resistivity suggests the negative temperature coefficient of resistance, depicting the semiconducting behavior of all the samples. Temperature variation of magnetization in terms of field cooled (FC) and zero field cooled (ZFC) curves shows the presence of two magnetic transitions in all the three samples. One pertains to paramagnetic to ferromagnetic transition temperature and another is due to downturn in magnetization at lower temperature. Sr doping also causes an increase in the magnetic ordering temperature. Field variation of magnetization shows the ferromagnetic nature of all the three samples, where the saturation magnetization decreases with increase in temperature as well as increase in Sr concentration. Temperature dependence of resistivity at different magnetic fields indicates the presence of magnetoresistance effect in all the three samples. These studies highlight the role of Sr doping in determining and influencing the various physical properties discussed in this paper and the importance of these double perovskite systems for future material design and various technological applications.

Nonlinear Acoustic Spin Pumping Caused by Temperature-Dependent Frequency Shifts of Surface Acoustic Waves

Nonlinear Acoustic Spin Pumping Caused by Temperature-Dependent Frequency Shifts of Surface Acoustic Waves