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Improved photocatalytic activity through cobalt (Co) doping has been reported for Al2O3 nanoparticles in this paper. Undoped and Co-doped Al2O3 nanoparticles have been synthesized via a precipitation method. Pure and Al2O3 nanoparticles exhibit a monoclinic crystal structure. The optical bandgap decreases from 3.80 eV to 3.64 eV with Co doping. Due to the red shift in the bandgap, the recombination rate of photo-induced electrons and holes decreases in the doped catalysts which improved their efficiencies against the degradation of rhodamine dye. A remarkable degradation efficiency of 95.45% is evinced for the 4 wt.% Co-doped Al2O3 catalyst and this was well acknowledged from its decreased crystallite size, decreased bandgap and increased photosensitivity values. An increased degradation rate constant value of 0.96649 min−1 observed for the 4 wt.% Co-doped Al2O3 catalyst also confirms this. The results obtained indicate that the Co-doped Al2O3 nanoparticles are potential candidates as visible light catalysts with remarkable degradation efficiencies against toxic dyes. Also, the realization of ferromagnetism confirms the regenerable and reusable quality of the Co-doped Al2O3 catalysts. [ABSTRACT FROM AUTHOR]

We investigate the magnetotransport properties of La0.7Ca0.3-xAgxMnO3 (0<=x<=0.3) polycrystalline films prepared by spray pyrolysis. The virgin La0.7Ca0.3MnO3 (LCMO) (x=0.0) film shows paramagnetic-ferromagnetic [insulator-metal (IM)] transition at TC∼260 K (TIM∼245 K). Ag doping induces appreciable enhancement in TC/TIM and interestingly TIM of Ag doped films is higher than the corresponding TC value. In the 30% Ag doped film IM transition occurs at ∼325 K which is ∼10 K higher than its TC∼315 K. Strong irreversibility is observed in zero field cooled–field cooled magnetization of all the films and the irreversibility temperature Tirr>TC increases with Ag doping. This suggests the formation of magnetic clusters above TC. The pure LCMO film exhibits small magnetoresistance (MR) ∼20% and rather poor temperature coefficient of resistance (TCR) in the vicinity of the room temperature. In contrast, around room temperature the Ag doped films show large MR which is ∼60% for x=0.15 and decreases to ∼30% for the pure Ag doped film. Ag doped films also have good TCR ∼4%/K in the vicinity of room temperature. [ABSTRACT FROM AUTHOR]

We have successfully synthesized a 1212-type niobio-cuprate with an ideal formula of NbSr2YCu2O8 by high-pressure and high temperature method. The phase-pure sample was obtained by Nb-poor Cu-rich starting composition, Nb0.9Sr2YCu2.1O7.9, at 6 GPa and 1450 °C for 2 h. The 1212-type niobio-cuprate has tetragonal lattices of a=3.853(1) Å and c=11.547(1) Å (space group P4/mmm), isostructural to Ru–1212Y phase. From magnetic measurements, it was found that superconductivity and weak ferromagnetism coexisted below ∼17 K in the Nb0.9Sr2YCu2.1O7.9 sample, although the superconducting volume fraction is still very small. [ABSTRACT FROM AUTHOR]

We have successfully synthesized a 1212-type niobio-cuprate with an ideal formula of NbSr2YCu2O8 by high-pressure and high temperature method. The phase-pure sample was obtained by Nb-poor Cu-rich starting composition, Nb0.9Sr2YCu2.1O7.9, at 6 GPa and 1450 °C for 2 h. The 1212-type niobio-cuprate has tetragonal lattices of a=3.853(1) Å and c=11.547(1) Å (space group P4/mmm), isostructural to Ru–1212Y phase. From magnetic measurements, it was found that superconductivity and weak ferromagnetism coexisted below ∼17 K in the Nb0.9Sr2YCu2.1O7.9 sample, although the superconducting volume fraction is still very small. [ABSTRACT FROM AUTHOR]

Ba-doped CdO (CdO:Ba) thin films with different concentrations of Ba (0, 1, 2 and 3 wt.%) were prepared on glass substrates by spray technique using perfume atomiser. The effect of Ba doping concentration on the structural, morphological, optical, photoluminescence and magnetic properties of the CdO films was investigated and the results obtained are presented in this work. Structural studies support the polycrystalline nature of the films. The direction of preferential growth of the CdO film along the (1 1 1) plane remain unaltered with Ba doping. Morphological studies show the presence of cauliflower-shaped structures for all the films. The optical transparency seems to be enhanced for the Ba-doped CdO films. The doped films exhibit ferromagnetic behaviour. The obtained results infer that barium, a cationic dopant ion, can enhance the optical and magnetic properties of CdO thin films. [ABSTRACT FROM AUTHOR]

This paper reports the role of bioactive elements in inducing ferromagnetism in CdO nanopowder. CdO nanopowder was synthesized by a soft chemical method using aloe vera gel extract as solvent. XRD studies confirm the presence of diffraction peaks related to cubic crystal structure of CdO. Weak peaks related to the oxides of Cu, Fe, Mg, Zn, Ni and Mn were also observed. Nanosized grains were observed from the TEM image. EDX and XPS spectra confirm the presence of bioactive magnetic elements in the synthesized sample. Magnetic studies confirm that the paramagnetic nature of CdO becomes ferromagnetic due to the presence of magnetic ions in the aloe vera gel extract. [ABSTRACT FROM AUTHOR]

In order to check the solubility of Zn in the (SrZn)CoO 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 multi-phased materials for (SrZn)CoO 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, T. All the present samples show soft ferromagnetism with T in the range of 272-285 K for 0.05≤ x≤0.3. The effective paramagnetic moment, P determined from the paramagnetic region decreases upon the substitution of Zn for Sr-site. These P (3.3-2.8 μ/Co) values for 0.05≤ x≤0.3 compositions seem to suggest that the Co lie in intermediate spin (IS) state for the present (SrZn)CoO series, although they are slightly smaller than those expected for IS-Co; P=3.87 μ/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, Δ H=90 kOe. The present research findings are compared with our previous results on different perovskite cobalt oxides. [ABSTRACT FROM AUTHOR]

In this present investigation, both YBaRuCuO and SrReCaCuO 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 YBaRuCuO and SrReCaCuO 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 at ∼450 K whereas the YBaRuCuO 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 and the effective paramagnetic moment, p obtained from the linear region of χ( T) plots are found to be −307.25 K and 3.74 μ/Ru, respectively, for the YBaRuCuO compound. The negative sign of θ 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 YBaRuCuO compound is a new approach and quite different from the routine conventional solid state synthesis approach. [ABSTRACT FROM AUTHOR]

The magnetic, transport and specific heat measurements of 1212-type compounds crystallized in tetragonal symmetry with starting composition, Cu2.1 LnNb0.9O7.9Sr2; Ln = Er, Dy have been investigated. The Cu2.1 LnNb0.9O7.9Sr2; Ln = Er, Dy compounds showed non-superconducting properties down to 1.8 K in the magnetic susceptibility measurements. The magnetic parameter ( μeff) obtained from the linear region of inverse molar magnetic susceptibility curves agrees with the calculated values for the respective free trivalent Er and Dy ions in Cu2.1 LnNb0.9O7.9Sr2; Ln = Er, Dy compounds. Though there is no strong evidence of magnetic ordering seen from magnetic susceptibilities, the hysteresis, M( H) curve obtained at 1.8 K looks like a canted antiferromagnet. The S-shaped (slightly curved) magnetization curve suggests weak ferromagnetic interactions that exist in the Ln = Er compound. A small hysteresis is observed with the coercive field ( Hc) of 49 Oe and the remnant magnetization ( Mr) of about 0.06 μB/f.u. for Ln = Er. Interestingly, such a hysteresis loop opening is not seen for the Ln = Dy compound. While specific heat anomaly ( λ-like transition) was observed for Ln = Dy compound at low temperature (around 6 K), for Ln = Er compound such an anomaly was not seen in the specific heat measurements. The electrical resistivity versus temperature, ρ( T), data showed that the compounds Cu2.1 LnNb0.9O7.9Sr2; Ln = Er, Dy are not in metallic state and they are really semiconducting-in-nature. Interestingly, rather large magnetoresistance, MR (∼18%) was observed at low temperature ∼2 K for Er-based niobio-cuprate. [ABSTRACT FROM AUTHOR]

In this brief article, structural, magnetization studies of oxygen deficient perovskite cobalt oxides CoSrO3− δ synthesized in two different ways are reported. The structural refinements (JANA2006) of X-ray powder diffraction data indicate that the sample prepared under ambient pressure ( stage-1) shows a hexagonal structure with P63/ mmc (194) as a possible space group. The stage-1 sample subsequently sintered at 1450 °C for 1–2 h under high-pressure 6 GPa conditions ( stage-2) crystallizes in tetragonal symmetry with I4/ mcm (140) space group having a=5.444(7) Å and c=7.68(2) Å. While the stage-1 sample exhibits a paramagnetic nature in the magnetic susceptibility, M( T), measurements, interestingly the sample annealed under high-pressure conditions shows ferromagnetism in the magnetic susceptibility, M( T) and field dependence magnetization, M( H) measurements. The high-pressure annealed sample shows hysteresis opening with a quite large coercive field of 7.3 kOe at 1.8 K. The temperature dependence of the inverse molar susceptibility curves exhibits linear behavior in the high-temperature regime and could be fitted to the Curie–Weiss expression, χ( T)= C/( T− θW). The experimental values of θW and peff obtained from the linear region of the inverse molar magnetic susceptibility curves are found to be: −210.7(5) K and 2.38(2) μB/Co for stage-1 and 260.2(7) K and 1.87(3) μB/Co for stage-2 samples, respectively. A negative sign of θW indicates rather strong antiferromagnetic correlations in the stage-1 sample. Apart from these results, the structural parameters reported by various groups for the strontium-based perovskite cobalt oxides are also presented in the form of literature collections. [ABSTRACT FROM AUTHOR]

57Fe (1%) doped SrCoO3 obtained by high-pressure method, has been investigated by magnetization and Mössbauer spectroscopy studies (MS) in the temperature range 4.2 K to 300 K. The ferromagnetic ordering temperature T C obtained is 272(2) K. Isothermal magnetization curves have been measured at various temperatures, from which the saturation moments ( M sat) have been deduced. The 57Fe MS spectra display standard six-line patterns with an isomer shift typical of Fe3 + and a very small quadrupole splitting (QS = 0.14(1) mm/s above T C). The magnetic hyperfine field at 4.2 K is 276(1) kOe. The temperature dependencies of the iron hyperfine field and M sat (1.83 µ B at 5 K) are almost identical. This shows that the Fe3 + is replacing Co4 + , both of the same electronic configuration. They also interact similarly, namely the Fe–Co exchange is almost identical to the Co–Co exchange. [ABSTRACT FROM AUTHOR]

Abstract: We report synthesis and magnetization of MSr2Y1.5Ce0.5Cu2O10 (M/Y-1222) compounds with M = Ru, Mn and Cr by HPHT. They are synthesized at high-pressure of 6 GPa in optimized temperatures of up to 1450 °C, for Ru, Mn and 1550 °C in the case of Cr based Y/1222, for a time duration of three hours for all the samples. All the samples crystallized with tetragonal structure in I4/mmm space group. Few minor impurities are also seen in the case of Mn,Cr/Y-1222 samples. DC magnetic susceptibility measurements exhibited ferromagnetic like transition for all the three compounds at low temperatures. At 5 K, the magnetization M(H) experiments showed clear ferromagnetic like hysteresis loops for Ru and Mn samples with sizeable returning moment (M r) and coercive field (H c). In the case of Cr/Y-1222 system though, ferromagnetism is visible below around 45 K in susceptibility measurements, the characteristic M r and H c are not seen. To the best of our knowledge the Mn,Cr/Y-1222 phases are synthesized for the first time and the quality of our earlier reported Ru/Y-1222 is improved. [Copyright &y& Elsevier]

Abstract: Polycrystalline perovskite cobalt oxides Sr1– xRx CoO3 (R=Y and Ho; ) were prepared by high-pressure/high-temperature technique. X-ray powder patterns of the Y-system indicated cubic perovskite form for , and orthorhombic perovskite form for and 1.0, while coexisting of the two phases for . The cubic perovskite samples had metallic electric resistivities while the orthorhombic ones with semiconducting or insulating nature. The parent compound SrCoO3 showed a ferromagnetic transition at 266K. With the Y substitution, the transition temperature increased slightly to ∼275K at , then decreased rapidly to ∼60K for . The YCoO3 () sample showed non-magnetic behavior. The Ho-substituted system showed quite similar structural, transport and magnetic properties to those of the Y-system. [Copyright &y& Elsevier]

Abstract: Polycrystalline perovskite cobalt oxides (Sr1– x Ca x )CoO3 (0⩽x⩽0.8) were synthesized under high pressure (6GPa) and high temperature (1200–1300 °C) conditions. Powder X-ray diffraction data confirmed that they have cubic perovskite structures. The end member of the solid solution, SrCoO3, exhibited a ferromagnetic transition with Curie temperature of and metallic electric conductivity. With increasing the Ca content , increased slightly to 286K at then decreased rapidly to 148K for . The origin of the ferromagnetism is discussed in relation to the spin state of the Co4+ ions. The present system showed a relatively large (∼5.5%) negative magnetoresistance for or 0.2 in the vicinity of T c. [Copyright &y& Elsevier]

In this paper, we report the synthesis, magnetotransport features, and magnetization of polycrystalline La2/3Ca1/3MnO3:Agx/Inx composites with x = 0, 0.1, 0.2, 0.3 and 0.4. In the case of La2/3Ca1/3MnO3:Agx, the temperature coefficient of resistance (TCR) near ferromagnetic (FM) transition enhances significantly with the addition of Ag. The FM transition temperature (TFM) is also increased slightly with Ag doping. Magnetotransport measurements revealed that magnetoresistance (MR) is found to be maximum near TFM. Very sharp TCR is seen near TFM with the highest value of up to 15 % for an Ag (0.4) sample, which is an order of magnitude higher than for pristine sample and is the best value yet reported for any polycrystalline LCMO compound. Increased TCR, TFM, and significant above room temperature MR of La2/3Ca1/3MnO3:Agx composites is explained on the basis of improved grains size. Interestingly the La2/3Ca1/3MnO3:Inx composites behaved exactly in the opposite way, resulting in decreased TFM, and TCR compared to the pristine LCMO compound. In fact, the grains morphology of LCMO:Inx composites is seen to be inferior to pristine LCMO which is opposite of the LCMO:Agx case. [ABSTRACT FROM AUTHOR]

Sr-doped SnS 2 nanopowders with 0, 5, 10 and 15 wt.% Sr concentrations were synthesized by a simple soft chemical route. XRD studies confirm the polycrystalline nature of the samples. The undoped and doped SnS 2 nanopowders exhibit hexagonal crystal structure with a strong (1 0 1) preferential orientation. The 2θ values of the (1 0 1) plane of the undoped SnS 2 shift towards lower angle with Sr doping. Nanoneedles are evinced for all the samples from the SEM images. EDX spectra confirm the presence of Sr in the doped samples. The optical band gap of pure SnS 2 decreases with Sr doping. Peaks related to SnS 2 are evinced at 572 nm in the PL spectra and at 313 cm −1 and 203 cm −1 in the Raman spectra. Improved ferromagnetic orderings in the form of S-shaped loops were observed for the doped samples. Antibacterial studies show that the zone of inhibition of SnS 2 increases with Sr-doping. The obtained results infer that Sr 2+ , a cationic dopant ion strongly enhanced the physical properties of SnS 2 nanopowders. [ABSTRACT FROM AUTHOR]

57Fe (1%) doped SrCoO3 obtained by high-pressure method, has been investigated by magnetization and Mössbauer spectroscopy studies (MS) in the temperature range 4.2 K to 300 K. The ferromagnetic ordering temperature T C obtained is 272(2) K. Isothermal magnetization curves have been measured at various temperatures, from which the saturation moments ( M sat) have been deduced. The 57Fe MS spectra display standard six-line patterns with an isomer shift typical of Fe3 + and a very small quadrupole splitting (QS = 0.14(1) mm/s above T C). The magnetic hyperfine field at 4.2 K is 276(1) kOe. The temperature dependencies of the iron hyperfine field and M sat (1.83 µ B at 5 K) are almost identical. This shows that the Fe3 + is replacing Co4 + , both of the same electronic configuration. They also interact similarly, namely the Fe–Co exchange is almost identical to the Co–Co exchange. [ABSTRACT FROM AUTHOR]