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The critical behavior and magnetocaloric effect (MCE) in the perovskite system La0.7−xPrxBa0.3MnO3 (x = 0.05, and 0.15) have been carefully investigated via dc-magnetization measurement. With the increase in Pr-doping, the universality class shifts from the predicted 3d-Heisenberg model characterized by a short-range coupling [β = 0.371 ± 0.008, γ = 1.351 ± 0.002 and δ = 4.634 ± 0.002, for x = 0.05] to an unknown one [β = 0.385 ± 0.004, γ = 1.324 ± 0.001 and δ = 4.435 ± 0.006, for x = 0. 15]. The critical exponents, however, obey the scaling behavior for both samples. Likewise, this series of compounds displays rescaled magnetic entropy data that plead in favor of a non-universal MCE behavior. Moreover, the field dependence of the magnetic entropy change (ΔSM) gives rise to critical exponents (β and γ) which are not consistent with that estimated through the critical behavior. Unexpectedly, the renormalization group approach revealed critical exponents for both samples comparable to those calculated for 3dXY spin interactions. All three exponents vary with Pr concentration, indicating the violation of both universality and weak universality hypotheses that may lead to several critical points. The unconventional outcomes suggest that, in addition to the correlation between quenched disorder and accommodation strain, magnetic anisotropy plays a major role with increasing Pr − x, opposing the exchange mechanisms. Pr − x enhanced the peak of ΔSM around TC and the relative cooling power (RCP). The broad operating temperature range along with a negligible hysteresis make Pr − 15% a promising candidate for magnetic refrigerant material near room temperature. [ABSTRACT FROM AUTHOR]

The structure, magnetic properties, and critical behavior of Nd0.6Sr0.2K0.2MnO3 compound are investigated. Rietveld refinement of the X-ray diffraction pattern shows that the examined sample is a pure single phase, crystallized in an orthorhombic Pnma structure. The nanometric size of crystallites calculated using Williamson-Hall method is validated by transmission electron microscopy micrographs. Magnetic measurements indicate a second-order ferromagnetic (FM)/paramagnetic (PM) transition at the Curie point Tc. Various techniques are used such as modified Arrott plot (MAP), Kouvel-Fisher method (KF), and critical isotherm analysis (CIA) to identify critical properties from isothermal magnetization data near critical regions. The deduced values are close to the 3D Ising model, proving the existence of a short-range ferromagnetic order in Nd0.6Sr0.2K0.2MnO3 sample. The results fully meet the requirements of the universal scaling assumption, further confirming its accuracy. [ABSTRACT FROM AUTHOR]

Strombidae strombus seashells have been used as calcium precursors to prepare nanocrystalline hydroxyapatite (HAp) via a wet chemical route. The as-prepared HAp powder has been investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and complex impedance spectroscopy to examine the morphology, elemental composition, crystal structure, functional groups, and electric properties. The synthesized HAp exhibits a single and nanocrystalline (23 nm crystallite size) hexagonal structure with lattice parameters a = 9.3819 ± 10–4 Å and c = 6.8927 ± 10–4 Å. FT-IR and Raman spectroscopy results confirm the presence of P−O, O− H, and C−O bonds. The AC conductivity is frequency and temperature-dependent. The activation energy values are in the range of 0.238−0.319 eV, and the conduction mechanism proceeds by proton hopping. The Nyquist plots are modeled by an equivalent circuit composed of (Rg//CPEg) + (Rgb//L//CPEgb) elements. [ABSTRACT FROM AUTHOR]

Thermoelectric materials are gaining popularity as one of the most effective solutions to the energy issue because of their capacity to create electricity from waste heat without polluting the environment. In this work, we interest in the thermoelectric properties in NaNbO3 thin film prepared by sol–gel method and deposited by spray pyrolysis. The structural analyze using X-ray diffraction proves an ideal Pm 3 ¯ m cubic structure. Using UV–visible spectroscopy analysis, we found that the studied material is a semiconductor material with a direct band gap Eg = 1.29 eV. Thanks to the structure of the electronic bands extracted using DFT calculation, we have estimated the charge carrier densities Nc and Nv (Nc = 4.91 × 1019 cm−3 and Nv = 8.37 × 1019 cm−3). Using the semi-classical Boltzmann theory, thermal, electrical and thermoelectric properties were investigated. An interesting result was obtained which makes consider NaNbO3 a promising candidate that could be used for thermoelectric devices. [ABSTRACT FROM AUTHOR]

Pure and 15% bismuth-doped cobalt spinel ferrites [CoFe2O4 (CFO) and Co0.85Bi0.15Fe2O4 (CBFO)] were synthesized by the auto-combustion method using glycine as the fuel agent. Both structural and morphological studies confirmed the nanosize criteria for both compounds with an increase in particle size when introducing bismuth ions. The insertion of non-magnetic ions in the A-site of CFO compound induced a decrease in the saturation magnetization due to the increase of the antiferromagnetic interactions. The biocompatibility of CFO and CBFO nanoparticles with two different human breast cancer cells (T47-D and MDA-MB-231) and one prostate cancer cell (PC3) was evaluated. The CBFO compound induced a higher cancer cell mortality with IC50 values of 61.12, 66.41 and 134.38 µM, for MDA-MB-231, T47-D and PC3 cancer cells, respectively. The cytotoxicity against normal human cells was found to be lower than 2% even for high CBFO particle concentrations. Accordingly, both prepared compounds could be considered as potential therapeutic agents against cancer cells. [ABSTRACT FROM AUTHOR]