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Zhao J.,Luoyang Normal College | Zhang X.,Luoyang Key Laboratory of Laser Spectroscopy Technology | Liu S.,Luoyang Key Laboratory of Laser Spectroscopy Technology | Zhang W.,Luoyang Key Laboratory of Laser Spectroscopy Technology | Liu Z.,Luoyang Key Laboratory of Laser Spectroscopy Technology
Journal of Alloys and Compounds | Year: 2013

In this paper, BiFe1-xNixO3 (x = 0, 0.05, 0.10, 0.15, 0.20, and 0.25) nanoparticles were synthesized by a sol-gel process X-ray diffraction (XRD), and Raman technique analysis showed that a rhombohedrally distorted BiFeO3 structure with compressive lattice distortion induced by the Ni substitution at Fe sites. Superconducting QUantum Interference Device (SQUID) results showed that, compared with BiFeO3 prepared under similar conditions, the magnetic properties were significantly enhanced at room temperature. The enhanced ferromagnetism was attributed to the size confinement effect of the nanostructures, the ferromagnetic exchange between the neighboring Fe3+ and Ni3+ ions, and the changing of the Fe-O-Fe bond angle. Superparamagnetism with blocking temperature of 10 K for BiFe0.95Ni0.05O3, 75 K for BiFe0.85Ni0.15O3, 125 K for BiFe 0.80Ni0.20O3, and 200 K for BiFe 0.75Ni0.25O3 was also observed. © 2013 Elsevier B.V. All rights reserved. Source


Liu Z.-J.,Luoyang Normal College | Liu Z.-J.,Luoyang Key Laboratory of Laser Spectroscopy Technology | Zhao J.-G.,Luoyang Normal College | Zhao J.-G.,Luoyang Key Laboratory of Laser Spectroscopy Technology | And 4 more authors.
Journal of Optoelectronics and Advanced Materials | Year: 2014

Bi1-xLaxFeO3 (x= 0.05, 0.1, 0.15, 0.2, and 0.25) nanoparticles were synthesized by sol-gel method, and the effects of La content on the structure and magnetic properties were investigated. X-ray diffraction and Raman analysis showed that the structure of La-doped BiFeO 3 was transformed from a rhombohedral to a orthorhombic with the increase of La content. This was also accompanied by an increase in the magnetization up to x=0.20 followed by a reverse trend at higher doping levels. The enhanced ferromagnetism might be attributed to the antiferromagnetic core and ferromagnetic surface of the nanoparticles, the increasing of canting angle, and the structural distortion. When the dopant concentration up to x=0.25, the decreased ferromagnetism might be attributed to the decreased of ferromagnetic component of canted Fe sublattice. Source


Zhang W.,Luoyang Normal College | Zhang W.,Luoyang Key Laboratory of Laser Spectroscopy Technology | Liu Z.,Luoyang Normal College | Liu Z.,Luoyang Key Laboratory of Laser Spectroscopy Technology | And 2 more authors.
Applied Surface Science | Year: 2012

ZnO:Fe powders have been prepared by sol-gel method with different calcination temperatures (650°C, 750°C, 850°C and 950°C). The crystal structures and optical properties were investigated by X-ray diffraction (XRD), Raman spectra and Photoluminescence (PL). The XRD results demonstrated that all of the samples were hexagonal wurtzite structure, and with the increase of calcination temperature, the diffraction peak of (0 0 2) slightly shifts to larger degree. Furthermore, the lattice vibrations have been investigated by Raman spectra, with the increase of calcination temperature, the representative peak E 2 high of ZnO shifts from 437.5 to 434 cm -1, corresponding to degradation of crystalline quality. Also, the dependence of PL spectra on calcination temperature has been investigated detailed. © 2012 Elsevier B.V. All rights reserved. Source


Zhang W.,Luoyang Normal College | Zhang W.,Luoyang Key Laboratory of Laser Spectroscopy Technology | Zhao J.,Luoyang Normal College | Zhao J.,Luoyang Key Laboratory of Laser Spectroscopy Technology | And 2 more authors.
Applied Surface Science | Year: 2013

Zn1-xFexO (x = 0.02, 0.04, 0.06, 0.08, 0.10) powders have been synthesized by sol-gel approach from Zn nitrate and Fe nitrate reduced by citrate. Their structural and optical properties have been investigated by X-ray diffraction (XRD), Raman spectra and photoluminescence (PL), respectively. XRD shows that Zn1-xFexO samples are single phase with the ZnO wurtzite structure as the Fe content is no more than 2%, while when Fe concentration reaches 4%, a secondary phase ZnFe2O4 is observed. Raman results show that the crystalline quality become worse with increasing of Fe concentration. PL spectra demonstrate that plenty of oxygen vacancy (VO) defects exist in the material. Superconducting quantum interference device (SQUID) shows room ferromagnetic behavior of sample Zn 0.98Fe0.02O at 300 K, while with the increasing of Fe content, ferromagnetism behavior disappears. © 2013 Elsevier B.V. All rights reserved. Source


Zhao J.,Luoyang Normal College | Zhao J.,Luoyang Key Laboratory of Laser Spectroscopy Technology | Liu S.,Luoyang Normal College | Liu S.,Luoyang Key Laboratory of Laser Spectroscopy Technology | And 4 more authors.
Journal of Nanoparticle Research | Year: 2013

In this work, Bi1-x Er x FeO3 (x = 0.05-0.25) nanoparticles were prepared by sol-gel method. X-ray diffraction and Raman analysis show that the structure of Er-doped BiFeO3 changes from rhombohedral lattice to orthorhombic one by increasing x. The remnant magnetization of the Bi1-x Er x FeO3 is significantly higher than those in BiFeO3 doped with non-magnetically rare-earth and it increases with increasing Er concentration. The enhanced magnetization was attributed to the suppression of the cycloidal spin structure by Er3+ substitution and the ferromagnetic interaction between Fe3+ and Er3+ ions. The variation of the magnetization with temperature is also discussed. © 2013 Springer Science+Business Media Dordrecht. Source

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