Magnetoelectric behavior of ferrimagnetic BixCo2−xMnO4 (x=0, 0.1 and 0.3) thin films

Thin films of Bi_xCo_2−xMnO₄ (x=0, 0.1 and 0.3) were grown on quartz, LaAlO₃ (LAO) and YBa₂Cu₃O₇ (YBCO) buffer layer coated LAO substrates by pulsed laser deposition (PLD). X-ray diffraction (XRD) and Raman scattering measurements showed that the thin films exhibit single phase polycrystalline cubic spinel structure on all the substrates. Near edge X-ray absorption fine structure (NEXAFS) studies confirmed the octahedral occupancy of the substituted Bi³⁺ ions. Temperature dependent zero-field cooled (ZFC) magnetization measurements show the ferrimagnetic (FM) behavior (T_C∼186 K) and magnetization undergoes a crossover from positive to negative, owing to the opposite contributions of magnetic moments from Co and Mn ions. A weak ferroelectric property exhibited by the films above room temperature was evidenced through the capacitance-voltage (C-V) and dielectric measurements. Magnetoelectric coupling was found to be maximum just below FM-T_C.     

Thermal Decomposition Studies of Mixed Rare Earth Hydrogen Selenite Crystals

Mixed rare earth hydrogen selenite crystals, neodymium praseodymium hydrogen selenite (Nd_xPr_1−x(HSeO₃)(SeO₃)⋅2H₂O), Neodymium samarium hydrogen selenite (Nd_xSm_1−x(HSeO₃)(SeO₃)⋅2H₂O) and praseodymium samarium hydrogen selenite (Pr_xSm_1−x(HSeO₃)(SeO₃)⋅2H₂O) were prepared by gel diffusion technique. Simultaneous thermogravimetric and differential thermal analysis were carried out on the grown crystals. Decomposition is observed to occurs in six steps, which gives the evidence of successive losses of H₂O and SeO₂. The final product due to decomposition is a mixed rare earth oxides. FT-IR spectrum of the crystal samples heated at different temperatures complemented to the TG-DTA results. This revised version was published online in July 2006 with corrections to the Cover Date.     

Detecting functional magnetic resonance imaging activation in white matter: Interhemispheric transfer across the corpus callosum

Background  

It is generally believed that activation in functional magnetic resonance imaging (fMRI) is restricted to gray matter. Despite this, a number of studies have reported white matter activation, particularly when the corpus callosum is targeted using interhemispheric transfer tasks. These findings suggest that fMRI signals may not be neatly confined to gray matter tissue. In the current experiment, 4 T fMRI was employed to evaluate whether it is possible to detect white matter activation. We used an interhemispheric transfer task modelled after neurological studies of callosal disconnection. It was hypothesized that white matter activation could be detected using fMRI.     

Temperature-dependent AC electrical conductivity,thermal stability and different DC conductivity modelling of novel poly(vinyl cinnamate)/zinc oxide nanocomposites

Thermal analysis on organically modified Ca²⁺-montmorillonite (OMON) and its source materials—octadecylamine (ODA) and Ca²⁺-montmorillonite (Ca²⁺-Mon)—was studied using thermally stimulated current (TSC) technique. The appearance of ρ _MON peak with the T _max = 75 °C shows the ability of the developed TSC system to demonstrate the relaxation effects of dehydration in Ca²⁺-Mon. It appeared within the temperature range of DSC endothermic peak (30–100 °C) where the T _mMON = 58 °C. Segmental motions of ODA chains and structural disruptions in the modifier agent compound produced TSC α _ODA, ρ _ODA and ρ _1ODA peaks that are comparable to thermal transition and endothermic peaks in DSC profile (T _gODA, T _m1ODA and T _m2ODA). The effect of localized motion in ODA chains as revealed by the TSC β_OMON peak (T _max = ?23 °C), however, is absent in the DSC profile of OMON. It shows TSC technique has high sensitivity in detecting various relaxation behaviors at molecular level. More evidences are demonstrated by the ρ _OMON (T _max = 86 °C) and ρ _1OMON (T _max = 105 °C) peak originated from the ODA chains structures. These peaks also confirm the intercalation of the modifier cations inside the Ca²⁺-Mon gallery.     

Synthesis of solid solutions of Mn and Bi substituted V2O5 and substitutional effect in structural and optoelectronic behavior

V₂O₅ is an attractive material with enormous technological applications such as cathode material in lithium batteries and electrochromic displays. Mn and Bi substitution in vanadium pentoxide (V₂O₅) was done by conventional solid state reaction technique with different composition. The chemical composition, structural and optical properties were investigated employing different techniques, such as XRD, SEM and UV-Vis Spectra. XRD studies exhibit the predominant (0 0 1) peak of orthorhombic phase. SEM image shows the uniformity of the material synthesized. Variable transmittance is exhibited by samples doped with different percentages of dopants. The dielectric property studies and ac conductivity measurements were carried out by Hioki LCR Hi-Tester.     

Thermal degradation, dielectric and magnetic studies on copper tartrate trihydrate crystals

Single crystals of copper tartrate trihydrate (CTT) with orthorhombic structure were grown in silica gel medium, by the controlled chemical reaction method. The Fourier transform infrared spectrum in the range 400–4,000 cm^?1 were recorded and the vibrational bands corresponding to different functional groups are assigned. Thermal stability of the grown crystals was investigated by differential thermal analysis, thermogravimetric and differential scanning calorimetry studies. The presence of water molecules and the dehydration stages are discussed. The dielectric studies on CTT crystals were performed in the frequency range of 100–5 MHz at three different temperatures which indicated that the dielectric constant decreases with frequency and increases with temperature. The ac conductivity is found to increase with frequency and temperature. The vibrating sample magnetometer studies on these crystals confirmed the diamagnetic nature of the CTT crystals.     

Thermal degradation and spectroscopic studies of single-crystalline organometallic calcium adipate monohydrate

Journal of Thermal Analysis and Calorimetry - Calcium adipate monohydrate single crystals were grown by single gel diffusion technique using silica gel as a medium of growth. The powder X-ray...