Showing papers by "Tran Dang Thanh published in 2010"
TL;DR: In this article, the structural, optical, and magnetic properties of Zn1−xMnxO nanorods were studied based on thermal diffusion and x-ray diffraction.
Abstract: We prepared Zn1−xMnxO nanorods by thermal diffusion. These samples were then studied the structural, optical, and magnetic properties. The structural analyses basing on x-ray diffraction and transmission electron microscope revealed the absence of Mn-related secondary phases. The study of photoluminescence spectra revealed the blueshift in the UV emission when the Mn doping concentration was increased, as a consequence of the extension of the band gap energy. Besides this situation, the increase in emission intensity associated with extrinsic defects at about 680 nm also took place. Concerning the Raman scattering spectra, apart from conventional phonon modes related to the ZnO wurtize-type structure, there were some additional modes introduced by the doping. Their origin was assessed carefully. Particularly, the shift in peak position of E2(high) toward low frequencies due to the increase in the Mn doping concentration could be explained well by means of the spatial correlation model. Magnetic measuremen...
36 citations
TL;DR: In this article, the effect of particle size on magnetic and electrical properties was investigated and a phenomenological model, describing competition between the FM and PI phases was used to elucidate temperature dependence of the resistivity with and without magnetic field, agrees quantitatively with experimental observations.
30 citations
TL;DR: In this paper, the electrical transport properties and magnetoresistance of La 0.7 Ca 0.3 MnO 3 /La 0.1 MnO3 composites are investigated as a function of sintering temperature.
26 citations
TL;DR: In this paper, the effect of grain size on low-field magnetoresistance (LFMR) has been investigated based upon a phenomenological model taking into account the spin-polarized transport across grain boundaries.
23 citations
01 Jan 2010
TL;DR: In this article, the structural, optical, and magnetic properties of ZnO nanorods were studied based on thermal diffusion and x-ray diffraction and transmission electron microscopy.
Abstract: We prepared Zn 1�x Mn x O nanorods by thermal diffusion. These samples were then studied the structural, optical, and magnetic properties. The structural analyses basing on x-ray diffraction and transmission electron microscope revealed the absence of Mn-related secondary phases. The study of photoluminescence spectra revealed the blueshift in the UV emission when the Mn doping concentration was increased, as a consequence of the extension of the band gap energy. Besides this situation, the increase in emission intensity associated with extrinsic defects at about 680 nm also took place. Concerning the Raman scattering spectra, apart from conventional phonon modes related to the ZnO wurtize-type structure, there were some additional modes introduced by the doping. Their origin was assessed carefully. Particularly, the shift in peak position of E2high toward low frequencies due to the increase in the Mn doping concentration could be explained well by means of the spatial correlation model. Magnetic measurements proved the samples with Mn concentrations above 1.15 at. % exhibiting the weak-ferromagnetic order at low temperatures. The nature of the ferromagnetism was discussed by means of the results of the structural and optical investigations. © 2010 American Institute of Physics. doi:10.1063/1.3478709
4 citations
TL;DR: In this paper, the effect of particle size on magnetic and electrical properties was investigated and a phenomenological model, describing competition between the FM and PI phases was used to elucidate temperature dependence of the resistivity with and without magnetic field, agrees quantitatively with experimental observations.
Abstract: Nanocrystalline samples of La0.7Ca0.3MnO3 were synthesized by reactive milling method and annealed at various temperatures. Effect of particle size on the magnetic and electrical properties was investigated. While the ferromagnetic–paramagnetic transition temperature TC does not show significant change, metal–insulator TMI is markedly affected by particle size. Experimental data indicates linear relationship of magnetization and resistivity to the surface/volume ratio of the particles with different mean sizes. A phenomenological model, describing competition between the FM and PI phases used to elucidate temperature dependence of the resistivity with and without magnetic field, agrees quantitatively with experimental observations.
1 citations