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- 1. J.Am.Chem.Soc. 130, 48 (2008) , ACS , “Enhanced Ferromagnetism and Tunable Saturation Magnetization of Mn/C Codoped GaN Nanostructures Synthesized by Carbothermal Nitridation”, Zeyan Wang, Baibiao Huang, Lin Yu, Ying Dai, Peng Wang, Xiaoyan Qin, Xiaoyang Zhang, Jiyong Wei, Jie Zhan, Xiangyang Jing, Haixia Liu, and Myung-Hwan WhangboMn/C-codoped GaN nanostructures were synthesized by carbothermal nitridation with active charcoal as the carbon source. Nanostructures such as zigzag nanowires and nanoscrews were observed by varying the reaction time and the C/Ga molar ratio of the starting material used for the synthesis. The structures and morphologies of the as-grown samples were characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy measurements. The doping of both Mn and C in the GaN matrix was confirmed by X-ray photoelectron spectroscopy measurements, and the ferromagnetic properties of Mn/C-codoped GaN samples were confirmed by room-temperature magnetization measurements. The saturation magnetization of Mn/C-codoped GaN increases steadily with increasing C/Ga molar ratio of the starting material at a rate of ~0.023 emu/g per C/Ga molar ratio, and the ferromagnetism of Mn/C-codoped GaN can be stronger than that of Mn-doped GaN by a factor of ~40. A plausible growth mechanism was proposed, and the role of carbon codoping in tuning the morphology and ferromagnetic property was discussed. Our work suggests that carbon doping in the GaN matrix favors the N sites over the Ga sites, Mn/C-codoping in the GaN matrix is energetically favorable, and the C-codoping strongly enhances the preference of the FM coupling to the AFM coupling between the two doped Mn sites. These suggestions were probed on the basis of first-principles density functional theory electronic structure calculations for a number of model doped structures constructed with a 32-atom 2 × 2 × 2 supercell. (Read more)
- 2. J. Phys. Chem. Solids 67, 789 (2006) , “Spectroscopic and magnetic studies of manganese ions in ZnO–Sb2O3–B2O3 glass system”, M. Srinivasa Reddy, G. Murali Krishna , N. VeeraiahZnO–Sb2O3–B2O3 glasses containing different concentrations of MnO ranging from 0 to 1.0 mol% were prepared. A number of studies, viz. optical absorption, infrared and ESR spectra and magnetic susceptibility, were carried out as a function of manganese ion concentration. The analysis of... (Read more)
- 3. Phys. Rev. B 69, 115210 (2004) , “Optical and magnetic properties of Mn in bulk GaN”, A. Wolos, M. Palczewska, M. Zajac, J. Gosk, M. Kaminska, A. Twardowski, M. Bockowski, I. Grzegory, S. PorowskiWe report results of electron paramagnetic resonance, magnetization, and optical absorption studies of bulk GaN crystals doped with Mn and, for some samples, codoped with Mg acceptor. The experiments performed show that the charge state of the Mn ion in GaN depends on the Fermi level position in the... (Read more)
- 4. J. Appl. Phys. 93, 9697-9702 (2003) , “Growth and characterization of GaN:Mn epitaxial films”, T. Graf, M. Gjukic, M. Hermann, M. S. Brandt, M. Stutzmann, L. Görgens, J. B. Philipp, O. AmbacherThe oxidation states of Mn in epitaxial GaN films grown by plasma induced molecular beam epitaxy were investigated by electron spin resonance (ESR), elastic recoil detection, superconducting quantum interference device magnetization, and photothermal deflection spectroscopy measurements. Comparison... (Read more)
- 5. Phys. Rev. B 63, 233202 (2001) , “Tetrahedral Mni4 Cluster in Silicon”, J. Wedekind, H. Vollmer, R. Labusch.Mni40 clusters were investigated by electron paramagnetic resonance in silicon specimens with initial doping concentrations between 1.5×1015?P cm-3 and 5×1016?B cm-3. In n-type samples and in intrinsic samples, we obtained the EPR... (Read more)
- 6. Phys. Rev. B 61, 1918 (2000) , “EPR investigation of manganese clusters in silicon”, J. Martin, J. Wedekind, H. Vollmer, and R. LabuschManganese centers were investigated in silicon specimens with initial doping concentrations between 1.5×1015 P cm-3 and 6×1015 B cm-3. All known Mn centers could be observed but the cluster Mni3Mni was missing in highly-boron-doped... (Read more)
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