Magnetic properties of mixed-spin- (5/2,1) systems in a hexagonal core-shell nanowire structure based on the Ising-like model with negative core-shell exchange interactions were investigated using the Mean-Field Approximation (MFA), based on the Gibbs-Bogoliubov inequality for free energy, along with Monte-Carlo simulations (MCS) employing the heat bath (Metropolis) algorithm. The findings highlight the significant influence of the spin-5/2 core on the system's magnetic behavior, leading to phenomena such as one or two compensation temperatures, critical end points (CEPs), isolated critical points (ICPs), tricritical points (TCPs) and first- and second-order phase transitions. Furthermore, the effects of various exchange interactions and anisotropy parameters on the thermal phase diagrams were analyzed. The study also explored magnetic hysteresis behavior at low temperatures, revealing multiple transitions involving intermediate spin states and resulting in up to eleven distinct hysteresis loops. These different obtained features can contribute to opening new avenues for research and providing insights into magnetic nanoparticles.
We studied the magnetic and electronic properties of perovskite manganite ${ m Nd}_{0.6}{ m Sr}_{0.4}{ m MnO}_{3}$Nd0.6Sr0.4MnO3. The temperature-dependent magnetization M(T) and resistivity $ ho \lpar T par$rho(T) curves reveal a ferromagnetic-paramagnetic and metal-insulator phase transition at $T_{C}=264\, { m K}$TC=264 K, respectively. The critical behavior was investigated through various techniques such as modified Arrott plot, Kouvel-Fisher method and critical isotherm analysis. The magnetic data analyzed in the critical region using the above methods yield the critical exponents of $\beta =0.234$beta=0.234 and $\gamma =0.973$gamma=0.973. The exponent $\delta =5.07$delta=5.07 independently obtained from the critical magnetization isotherm was found to basically fulfill the Widom scaling relation $\delta =1+\gamma /\beta$delta=1+gamma/beta. Moreover, the critical exponents also obey the single scaling equation of $M\lpar H\comma\; \varepsilon par = \varepsilon <^>\beta f_\pm$M(H,epsilon)=epsilon beta f +/- $\lpar H/ \varepsilon <^>{\beta +\gamma } par$(H/epsilon beta+gamma). These results indicate that the obtained critical exponents are reliable. The values are very closed to the tricritical mean-field model rather than the universal theory, indicating that there may be a tricritical point in ${ m Nd}_{0.6}{ m Sr}_{0.4}{ m MnO}_{3}$Nd0.6Sr0.4MnO3 phase diagram.
This study investigates the thermal behavior and stability of pure phase change materials (PCMs) and their composites with expanded graphite (EG) using thermogravimetric analysis and derivative thermogravimetry. The impact of EG concentrations (5%, 10%, and 15%) and heating rates (5, 10, 15, and 20 degrees C/min) on thermal degradation was analyzed, revealing notable improvement in stability with increased EG content. Model-free kinetic analyses Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, Starink, and Tang and the model-fitting Coats-Redfern method were applied to estimate activation energy. Pure PEG 6000 exhibited Ea values between 106.03-115.86 kJ/mol, whereas composites with 15% EG achieved up to 203.15 kJ/mol. Thermodynamic parameters (Delta H, Delta S, and Delta G) reflected enhanced energy dynamics and reduced spontaneity. Maximum thermal conductivity of 1.8955 W/mK was recorded for the 15% EG composite. Artificial Neural Network modeling yielded R-2 > 0.996 across all datasets, demonstrating excellent agreement with experimental mass loss, thus supporting advanced PCM design for thermal energy storage.
This paper reports the study of charge transport in manganese (Mn) doped barium calcium titanate ceramics using ac conductivity and electric modulus analysis. Various parameters such as sigma dc, omega H and s have been extracted from the fitting of experimental ac conductivity considering the Almond-West law. With Mn doping, the values of activation energy for dc conduction (Edc) are found in the range 1.041-1.061 eV. The conduction in the studied ceramics occurs via Overlapping large Polaron tunneling model. Thermal activation energy of electrical conduction (Edc) has been found to decrease with Mn concentration. Parameters, viz. beta, M '' max and fmax, are evaluated by electrical modulus data fitting with KWW function. Values of beta confirm non-Debye-type relaxation behavior. The values of relaxation time (tau M '') in the range 0.42 mu s to 1620 mu s and decreases with temperature, indicating that the relaxation process is thermally activated and occurs faster at higher temperatures and increases with Mn & sup2;+ doping. The activation energy for relaxation (ER) are in the range from 1.21 eV to 1.34 eV.
This study presents a comprehensive analysis of the structural, electronic, and optical properties of the perovskite compounds KZrS3 and KZrSe3, employing state-of-the-art first-principles calculations based on Density Functional Theory (DFT). Structural optimizations were performed using the Perdew-Burke-Ernzerhof (PBE) functional within the Generalized Gradient Approximation (GGA), ensuring accurate modeling of their equilibrium configurations. The electronic band structure calculations reveal that both materials possess indirect band gaps, measured at approximately 0.81 eV for KZrS3 and 0.49 eV for KZrSe3. Analysis of the density of states (DOS) shows that the electronic states near the Fermi level are primarily derived from K and Zr orbitals, with relatively minor contributions from S and Se.The optical properties further emphasize the technological relevance of these materials. Both compounds exhibit strong absorption in the visible range and minimal optical losses, highlighting their potential for optoelectronic applications. These features make KZrS3 and KZrSe3 promising candidates for next-generation devices such as solar cells, photodetectors, and light-emitting diodes. Overall, the findings underscore the potential of these perovskites to play a significant role in advancing high-efficiency optoelectronic technologies.
This study described the structure and dielectric properties of Pb0.98-x Ba-x Ca (0.02) [(Zr-0.52 Ti-0.48)(0.94) - (Zn-1/3 Ta-2/3)(0.03) - (In-1/3 Sb-2/3)(0.03)] O-3 (PBC-ZTZTIS) ceramics (where x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05), were synthesized by a normal solid-state method and sintered at 1180 degrees C. The crystal structure, microstructure and dielectric properties of the ceramics were investigated via X-ray diffraction, Raman analyses, scanning electron microscopy and dielectric spectroscopy. X-ray diffraction results demonstrate that all the samples lie within the morphotropic phase boundary (MPB) region. Raman-active modes in PBC-ZTZTIS were identified through group theory analysis. Scanning electron micrographs of the samples show a uniform distribution of grain and grain boundaries. The optimum dielectric properties of PBC-ZTZTIS such as dielectric constant & varepsilon;(rmax) = 653805, Curie temperature Tc = 507 degrees C and the minimum dielectric loss (0.02%) were obtained at x = 0.03, which indicated that the PZT-BCZTIS ceramics are promising to lead to practical applications.
Thiourea ammonium carbonate (TAC), a novel semi-organic nonlinear optical single crystal, was successfully synthesized by the slow evaporation technique. The unit cell parameter of the grown crystal was revealed by single-crystal X-ray diffraction method. The molecular structure of TAC was determined by Fourier transform infrared (FTIR) spectroscopy. The lower cut-off wavelength (lambda = 328 nm) and the optical energy band gap (Eg = 3.92 eV) of the grown crystal were found by using UV-vis-NIR spectral analysis. The different morphological identities over the grown crystals were analyzed using scanning electron microscopy (SEM). The TAC crystal is suggested for the soft material category by the Vicker's microhardness tester. The corresponding dielectric properties were rigorously analyzed with different ranges of temperature. The optimum thermal stability of the TAC crystal was found by thermogravimetric analysis. The second-order generation efficiency was measured by Kurtz and Perry powder technique.
The present work reports the synthesis and characterization of a homologous series of new mesogens, 6-hexyloxy-2-(4-alkyloxybenzylideneamino) benzothiazoles with varied alkyl chain lengths (n = 5-10) at the terminal ether chain. The molecular structures of these mesogens were confirmed using H-1 and C-13 NMR (nuclear magnetic resonance) and FT-IR (Fourier transform infrared) spectroscopy. Their mesomorphic properties were examined using differential scanning calorimetry and polarized optical microscopy. All compounds appeared in a mesophase. Lower members of the series (n = 5), compounds displayed a single mesophase (nematic). An extra SmC phase and the nematic phase emerged when the alkoxy chain lengthened to (n = 6, 7, 8). These compounds exhibited only one mesophase (SmC), and the nematic phase disappeared as the transition progressed from the lowest member (n = 9) to the highest member (n = 10). DFT computations indicated that all compounds exhibit strong dipole moments and polarizabilities, which are critical for their mesogenic properties.
