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Balamurugan S.,Advanced Nanomaterials Research Laboratory
Journal of Superconductivity and Novel Magnetism | Year: 2012

In order to check the solubility of Zn in the (Sr 1-xZn x)CoO 3 perovskite structure and their research findings, several polycrystalline samples have been prepared under wide extreme synthesis conditions at 6 GPa/1300- 1650 °C. While 0.05 ≤ x ≤ 0.3 compositions revealed single phased cubic structure materials, x >0.3 showed multiphased materials for (Sr 1-xZn x)CoO 3 system. Like other substituted perovskite cobalt oxide systems (Ca, Y, Ho and Ce), the transport properties of the present materials show rather sizable changes with respect to 'x', although there are insignificant variations in lattice parameter and in Curie temperature, Tc. All the present samples show soft ferromagnetism with Tc in the range of 272-285 K for 0.05 ≤ x ≤ 0.3. The effective paramagnetic moment, Peff determined from the paramagnetic region decreases upon the substitution of Zn for Sr-site. These Peff (3.3-2.8 μB/Co) values for 0.05 ≤ x ≤ 0.3 compositions seem to suggest that the Co 4+ lie in intermediate spin (IS) state for the present (Sr 1-xZn x)CoO 3 series, although they are slightly smaller than those expected for IS-Co 4+; Peff = 3.87 μB/Co. The electrical resistivity is found to increase with increase of 'x' for the investigated samples. The temperature and field dependence of both positive and negative magnetoresistance (MR) are noted for the Zn substituted samples. About 5% of -MR is observed for x = 0.05 sample around the transition temperature (280 K) under the field strength difference, ΔH = 90 kOe. The present research findings are compared with our previous results on different perovskite cobalt oxides. ©Springer Science+Business Media, LLC 2012. Source


Balamurugan S.,Advanced Nanomaterials Research Laboratory
Journal of Nanoscience and Nanotechnology | Year: 2015

The Cu doped ZnO, (Zn1-xCuxO)O (x = 0.02, 0.04, 0.06, 0.08, and 0.1) nanomaterials were prepared by ball milling technique (BMT), citrate sol gel (CSG), and molten salt flux (MSF) methods. The various as-prepared (Zn1-xCux)O materials were analyzed by powder X-ray diffraction (pXRD), FTIR, and SEM-EDX measurements in order to check the phase formation, purity, surface morphology and elements present in the annealed materials. Due to the preparation methods as well as doping of 'x' slight variations in cell parameters are seen. The average crystalline size of CSG method shows smaller size (25∼35 nm) than BMT and MSF approaches. The materials obtained by MSF technique reveal the average crystalline size in the range of 32∼72 nm whereas the BMT materials exhibit 36∼50 nm for the composition, 0.02 ≤ x ≤ 0.1. The presence of functional groups and the chemical bonding in (Zn1-xCux)O system is confirmed through FT-IR measurements. It is evident from the FT-IR data that bands seen at 400∼500 cm-1 are characteristics of M-O (M = metal ion) bonding in the studied materials. The micro images observed by SEM exhibiting polycrystalline character as compared with the crystallite size obtained from XRD. Among the three approaches employed in the present investigations, in terms of average particle size the CSG method may be concluded as an efficient method for the preparation of Zn1-xCuxO nanomaterials. Copyright © 2015 American Scientific Publishers Source


Balamurugan S.,Advanced Nanomaterials Research Laboratory
International Journal of Modern Physics B | Year: 2012

The magnetic and transport properties of lightly Ce doped, Y 1-xCe xSr 2Ru 0.9Cu 2.1 O 7.9 (x = 0.05 and 0.1) samples have been studied and their results are compared with the pristine rutheno-cuprate, YSr 2Ru 0.9Cu 2.1O 7.9. The electron doping due to Ce 4+ for Y 3+ ion impacts on the physical properties of the present system. The tetragonal stabilized samples exhibit magneto superconducting properties under zero field cooled condition (H = 10 Oe) and the diamagnetic onset transition, T d shift slightly towards higher temperature with the increase of "x". Weak antiferromagnetic like hysteresis curves are seen for these samples at 2 K in the magnetic field strength up to ±10 kOe and the magnetization moment, M (μ B/Ru) decreases with increase of "x". While the magnetic property of the present system is due to canted Ru moments, the superconducting signal originates from CuO 2 plane. Through electrical resistivity measurements we observe that none of the samples exhibit bulk superconductivity down to 2 K. However the x = 0.05 sample reveals lowest resistivity in the entire temperature range than x = 0 and 0.1 samples. The isothermal magnetoresistance, MR(H) measured at different temperatures vary with tuning of "x". While x = 0.1 doped sample shows lower -MR (∼ 8%), the pristine sample exhibits maximum -MR (45%) at 2 K under ±90 kOe field condition. © 2012 World Scientific Publishing Company. Source


Balamurugan S.,Advanced Nanomaterials Research Laboratory
Journal of Superconductivity and Novel Magnetism | Year: 2016

We report here a simple solution combustion synthesis of nickel oxide (NiO) nanoparticles by using urea as a fuel and nickel nitrate as an oxidizer. The structural, morphological, optical, and magnetic properties of NiO nanoparticles were investigated by X-ray diffraction (XRD); highresolution scanning electron microscopy (HRSEM); Fourier transform infrared (FT-IR), nearinfrared (NIR), and UV-vis spectroscopic techniques; and vibrating sample magnetometer. The combustion-synthesized NiO nanoparticles have a cubic structure with an average crystalline size of ∼8 nm without any impurity. The agglomeration of fine particles with particle sizes in the range of 19.5 ∼22.4 nm is seen by HRSEM images. The FT-IR spectrum of NiO nanoparticles reveals that an absorption band at ∼493 cm −1 is due to the bending vibration of NiO phase. The NIR spectrum exhibits poor NIR reflectivity of the combustion product, NiO. The as-prepared combustion product was black in color in contrast to the usual light green color. The room-temperature magnetization of the as-prepared NiO nanoparticles reveals an antiferromagnetic behavior. © 2016 Springer Science+Business Media New York Source


Balamurugan S.,Advanced Nanomaterials Research Laboratory
Journal of Superconductivity and Novel Magnetism | Year: 2012

In this present investigation, both YBa 2Ru 0.85 Cu 0.15O 6 and Sr 2Re 0.69Ca 0.31CuO 6 perovskite compounds were prepared through high pressure/high temperature (HPHT) synthetic route. The as-prepared samples were structurally characterized by powder X-ray diffraction technique and their magnetic properties were measured. Both compounds crystallized in cubic symmetry with a different space group. The refined lattice parameter for the YBa 2Ru 0.85Cu 0.15O 6 and Sr 2Re 0.69Ca 0.31CuO 6 compounds are found to be a = 8.332(2) Å with space group, Fm- 3m (225) and a = 7.967(4) Å space group Pm-3m (221), respectively. The cuprate ordered perovskite compound shows ferromagnetism with high Curie temperature, T c at ∼450 K whereas the YBa 2Ru 0.85Cu 0.15O 6 compound reveals mixed magnetic natures below ∼170 K which is complicated by the presence of magnetic order in the Ru and Cu sublattices. Below 170 K, the compound shows two antiferromagnetic-like transitions (in ZFC mode) at ∼135 K and ∼60 K. With a further decrease of temperature (below 60 K), the susceptibility crosses negative (diamagnetic) signal at ∼35 K and shows maximum negative susceptibility at ∼11 K. By decreasing the temperature below 11 K, the negative susceptibility decreases and shows positive magnetic susceptibility at 2 K. In the fc mode curve, the sample shows broad antiferromagnetic like transition at ∼55 K. At low temperature (below 30 K), an increase in susceptibility signal is seen in the fc magnetic susceptibility curve. The magnetic parameters, such as Weiss temperature, θ w and the effective paramagnetic moment, p eff ob- tained from the linear region of χ -1(T ) plots are found to be -307.25 K and 3.74 μ B/Ru, respectively, for the YBa 2Ru 0.85Cu 0.15O 6 compound. The negative sign of θ w reveals the antiferromagnetic correlations of the compound. While these studied compounds are already known to the literature, the synthesis method (HPHT) employed for the present YBa 2Ru 0.85Cu 0.15O 6 compound is a new approach and quite different from the routine conventional solid state synthesis approach. © Springer Science+Business Media, LLC 2011. Source

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