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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. Phys. Rev. B 75, 195215 (2007) , “Effect of Co and O defects on the magnetism in Co-doped ZnO: Experiment and theory”, G. S. Chang, E. Z. Kurmaev, D. W. Boukhvalov, L. D. Finkelstein, S. Colis, T. M. Pedersen, A. Moewes, and A. DiniaThe electronic structure of Zn1−xCoxO (x=0.02, 0.06, and 0.10) diluted magnetic semiconductors is investigated using soft x-ray emission spectroscopy and first-principles calculations. X-ray absorption and emission measurements reveal that most Co... (Read more)
- 3. Phys. Rev. B 75, 193409 (2007) , “Magnetic properties of vacancies in a graphitic boron nitride sheet by first-principles pseudopotential calculations”, M. S. Si and D. S. XueWe use ab initio methods to calculate the magnetic properties of vacancies in a graphitic boron nitride sheet (g-BN). By applying a full spin-polarized description to the system, we demonstrate that the nitrogen vacancy (VN) or the boron vacancy (VB)... (Read more)
- 4. Phys. Rev. B 75, 144404 (2007) , “Ferromagnetism in Fe-doped ZnO nanocrystals: Experiment and theory”, Debjani Karmakar, S. K. Mandal, R. M. Kadam, P. L. Paulose, A. K. Rajarajan, T. K. Nath, A. K. Das, I. Dasgupta, and G. P. DasFe-doped ZnO nanocrystals are successfully synthesized and structurally characterized by using x-ray diffraction and transmission electron microscopy. Magnetization measurements on the same system reveal a ferromagnetic to paramagnetic transition temperature above 450 K with a low-temperature... (Read more)
- 5. Phys. Rev. B 75, 075312 (2007) , “Ferromagnetic to ferrimagnetic crossover in Cr-doped GaN nanohole arrays”, Q. Wang, Q. Sun, P. Jena, and Y. KawazoeUsing spin-polarized density-functional theory with exchange and correlation potential, approximated by both the generalized gradient approximation (GGA) and the GGA+U methods, we show that the coupling between a pair of Cr atoms substituted in GaN nanoholes is ferromagnetic. The interaction between... (Read more)
- 6. Phys. Rev. B 75, 035322 (2007) , “Ab initio study of electronic and magnetic properties of the C-codoped Ga1−xMnxN (100) surface”, Q. Wang, Q. Sun, and P. JenaFirst principles calculations based on gradient corrected density functional theory have been carried out to study the magnetic coupling between Mn atoms in pure and carbon doped Ga1−xMnxN thin films. We show that the ground state of Mn-doped GaN (100) thin... (Read more)
- 7. Phys. Rev. Lett. 98, 137202 (2007) , “Magnetizing Oxides by Substituting Nitrogen for Oxygen”, I. S. Elfimov, A. Rusydi, S. I. Csiszar, Z. Hu, H. H. Hsieh, H.-J. Lin, C. T. Chen, R. Liang, and G. A. SawatzkyWe describe a possible pathway to new magnetic materials with no conventional magnetic elements present. The substitution of nitrogen for oxygen in simple nonmagnetic oxides leads to holes in N 2p states which form local magnetic moments. Because of the very large Hund's rule coupling of... (Read more)
- 8. Phys. Rev. B 74, 235208 (2006) , “Theoretical study of the magnetism of Mn-doped ZnO with and without defects”, D. Iuan, B. Sanyal, and O. ErikssonWe calculate the exchange interaction parameters of a classical Heisenberg Hamiltonian for Mn-doped ZnO (Mn concentration between 5% and 20%) by an ab initio Korringa-Kohn-Rostoker coherent-potential-approximation method in the framework of density functional theory. A weak antiferromagnetic... (Read more)
- 9. Phys. Rev. B 74, 235207 (2006) , “Vacancy-enhanced ferromagnetism in Fe-doped rutile TiO2”, Jun Chen, Paul Rulis, Lizhi Ouyang, S. Satpathy, and W. Y. ChingBased on a series of supercell density functional calculations of Fe-doped TiO2 both with and without O vacancy (VO), we show that VO plays an important role in determining the magnetic properties of the dilute magnetic semiconductors (DMS). Without... (Read more)
- 10. Phys. Rev. B 74, 233201 (2006) , “Electronic and magnetic properties of V-doped anatase TiO2 from first principles”, Xiaosong Du, Qunxiang Li, Haibin Su, and Jinlong YangWe report a first-principles study on the geometric, electronic, and magnetic properties of V-doped anatase TiO2. The DFT+U (Hubbard coefficient) approach predicts semiconductor band structures for Ti1−xVxO2 (x=6.25% and... (Read more)
- 11. Phys. Rev. B 74, 174407 (2006) , “Superexchange in dilute magnetic dielectrics: Application to (Ti,Co)O2”, K. Kikoin and V. FleurovWe extend the model of ferromagnetic superexchange in dilute magnetic semiconductors to the ferromagnetically ordered highly insulating compounds (dilute magnetic dielectrics). The intrinsic ferromagnetism without free carriers is observed in oxygen-deficient films of anatase TiO2 doped... (Read more)
- 12. Phys. Rev. B 68, 125204 (2003) , “Magnetic properties of substitutional 3d transition metal impurities in silicon carbide”, M. S. Miao and Walter R. L. LambrechtUsing the linearized muffin-tin orbital (LMTO) method within both the atomic sphere approximation and full potential (FP) implementations and within the local spin-density-functional method and a supercell approach, we study the magnetic properties of cubic (3C) silicon carbide (SiC) doped by... (Read more)
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