Effect of Sodium Doping on Thermal Properties of Perovskite RMnO3 for Potential Magnetoelectric Applications

The partial replacement of rare earth cation by sodium introduces large size and charge mismatch at A-site affecting the bulk modulus and thermal properties of RMnO3 which in turn makes them suitable candidates for thermoelectric applications. Thermal, elastic, cohesive properties of sodium doped Rare Earth manganites R1-xNaxMnO3 (R3+= La, Pr, Tb) has been studied by means of a Modified Rigid Ion Model (MRIM) and AIM theory. Lattice specific heat (Cp) of Pr0.8Na0.2MnO3, and Tb0.85Na0.15MnO3 as a function of temperature (1K£T£ 350K) is found to be in agreement with the published data. The trend of variation of Debye temperature (?D), thermal expansion (?), bulk modulus (B) and cohesive energy (?) with A-site cationic radius is predicted probably for the first time for these technologically important doped rare earth manganites. Keywords: Thermal Expansion, Specific Heat, Thermal properties, Colossal Magnetoresistance Materials, Magnetoelectric materials

Thermoelastic Properties of Superoxide

We have applied an Extended Three Body Force Shell Model (ETSM) by incorporating the effect of translational- rotational coupling for the investigation of thermoelastic properties such as cohesive energy(??, molecular force constant(f), compressibility(b), Restrahlen frequency (??), Debye temperature (qD), Gruneisen parameter (g), second Gruneisen parameter (q), Moelwyn Hughes constants (F1), and ratio of volume expansion coefficient (av) to volume specific heat (cv ) of superoxide materials NaO2 and KO2 at 300K. Besides this we have calculated static shear modulii (c44). The shear modulii computed between the temperatures ranges 50K to 500K. Here, we could compare our result with experimental data for thermal properties only at room temperature and the magnitudes of SOECs seem to be correct, also the ETSM method produces the sign of SOECs correctly. Keywords: Orientationally Disordered Materials, Shear modulii, ETSM, TR coupling, Elastic constants] PACS: 62.60.bc,; 65.50-

Double Peak Behavior of Resistivity-Temperature Curves in (Nd / Pr)0.67Sr0.33MnO3 Manganites

We have reported the synthesis of polycrystalline samples of R0.67Sr0.33MnO3 (R Pr, Nd) from the precursors of PrMnO3, NdMnO3 and SrMnO3 by using solid state reaction method. These samples were sintered at 1200 °C and 1400 °C. Some of samples were also undergone oxygen annealing at 950 °C for 6 h. All the synthesized samples were characterized by X-Ray diffraction (XRD) technique, scanning electron microscopy (SEM) and low temperature resistivity versus temperature (R-T) measurement. The XRD patterns show the monophasic nature of the sintered and annealed samples. The sintered samples of Nd0.67Sr0.33MnO3 has metal- insulator transition at 250 K, while the sample annealed in oxygen shows two peaks, one sharp peak at 250 K and other broad peak at 200 K. The sintered samples of Pr0.67Sr0.33MnO3 has only one peak at 290 K, while the sample annealed in oxygen shows two peaks, one sharp peak at 290 K and another broad peak at 225 K. The two peak behavior in the annealed samples has been explained by inhomogeneous diffusion of oxygen in the core of the grain and at the grain boundaries region When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3596

Thermodynamic Properties of Ni-substituted LnCoO3 Perovskite

With the objective of exploring the unknown thermodynamic properties of Ni-substituted LnCoO3 perovskite, we present here an investigation of the temperature-dependent (10K < T < 300K) specific heat of LnCo0.95Ni0.05O3 (Ln=Pr and Nd) family. We report here probably for the first time the specific heat along with other elastic and thermal properties of Ni doped perovskite cobaltate LnCoO3 (Ln=Pr and Nd). In addition, the results on the cohesive energy (f) in orthorhombic perovskite phase, molecular force constant (ƒ), Reststrahlen frequency (uo) and Gruneisen parameter (γ) are also presented. Keywords: Specific heat, Bulk modulus, Perovskite cobaltat

Measurement of D0-D0 mixing and search for CP violation in D0→K+K-,π+π- decays with the full Belle data set

We report an improved measurement of D0 – D‾0 mixing and a search for CP violation in D0 decays to CP -even final states K+K− and π+π− . The measurement is based on the final Belle data sample of 976 fb −1 . The results are yCP=(1.11±0.22±0.09)% and AΓ=(−0.03±0.20±0.07)% , where the first uncertainty is statistical and the second is systematic

Cohesive and thermoelastic properties of 〖(KCN)〗_(x ) 〖(KCl)〗_(1-x)

The thermal and elastic properties of are investigated by means of Extended Three Body Force Shell Model (ETSM). The motion of constituent atoms or molecules or the nature of binding forces of a crystal can be investigated by exploring the mechanical properties of pure and mixed crystals like anharmonic elastic properties. We have chosen different compositions at different temperature to show that anharmonic elastic properties are temperature dependent rather than composition dependent and the purpose of study is to test the mechanical stabilities of the potential. Moreover, the thermodynamic properties such as molecular force constant (f), Reststrahlen frequency (uo), cohesive energy (f), Debye temperature (θD) and Gruneisen parameter (γ) have also been discussed. Keywords: Elastic constants, Cohesive energy, Thermodynamic propertie

Giant magneto resistance and temperature coefficient of resistance in Sm0.55Sr0.30Ag0.15MnO3 perovskite

Silver ions substituted samarium strontium manganite (Sm0.55Sr0.30Ag0.15MnO3) pervoskite was synthesized by using respective oxides in stoichiometric ratio through solid state reaction. The as-prepared sample was characterized by various analytical techniques to confirm its formation and understand the effect of monovalent silver ions in pervoskite lattice. X-ray diffraction pattern confirms the single phase formation while grain morphology in SEM image indicates good connectivity among the grains. The enhancement in metal to insulator transition temperature shows quenched disorder and magnetoresistance phenomena. The magnetoresistance (MR) and temperature coefficient of resistance (TCR) emerge from grain growth factor and homogeneity induced by Ag+ ions in the lattice. The reduction in hysteresis loss resulted from antiferromagnetic - ferromagnetic (TN) and ferromagnetic - paramagnetic (Tc) transitions reveals the removal of disorder in perovskite lattice by Ag+ ions substitution. This increases the magnetic moment across distinct ions on the applying magnetic field. The rise in MR% (~99%) with silver doping emerging from smooth spin tunneling of the grains across the boundary and suppression of the disordered magnetic fluctuations with increase in magnetic field has been reported. The present compound exhibits the first order nature of magnetism and observed first time the highest value of TCR ~ 95%