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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. Appl. Phys. 101, 013902 (2007) , “An electron paramagnetic resonance study of n-type Zn1−xMnxO: A diluted magnetic semiconductor”, A. Ben Mahmoud, H. J. von Bardeleben, J. L. Cantin, E. Chikoidze, and A. MaugerWe present the results of an electron paramagnetic resonance study of homogeneous single phase Zn1−xMnxO thin films with Mn concentrations varying between x=0.07 and x=0.34. Our results show antiferromagnetic (AF) coupling in the entire... (Read more)
- 3. Phys. Rev. B 75, 195335 (2007) , “Computational and experimental imaging of Mn defects on GaAs (110) cross-sectional surfaces”, A. Stroppa, X. Duan, M. Peressi, D. Furlanetto, and S. ModestiWe present a combined experimental and computational study of the (110) cross-sectional surface of Mn δ-doped GaAs samples. We focus our study on three different selected Mn defect configurations not previously studied in detail, namely surface interstitial Mn, isolated and in pairs, and... (Read more)
- 4. Phys. Rev. B 75, 115113 (2007) , “Structural, electronic, and magnetic properties of Mn-doped Ge nanowires by ab initio calculations”, J. T. Arantes, Antônio J. R. da Silva, and A. FazzioUsing ab initio total energy density-functional theory calculations, we investigated the electronic, structural, and magnetic properties of manganese-doped germanium nanowires. The nanowires have been constructed along the [110] direction and the dangling bonds on the surface have been... (Read more)
- 5. Phys. Rev. B 75, 115111 (2007) , “Spin dynamics in a weakly itinerant magnet from 29Si NMR in MnSi”, M. Corti, F. Carbone, M. Filibian, Th. Jarlborg, A. A. Nugroho, and P. Carretta29Si NMR spectra and nuclear spin-lattice relaxation rate measurements in MnSi paramagnetic phase are presented. The experimental results are analyzed in the framework of the self-consistent renormalization theory for spin fluctuations, and detailed estimates of microscopic parameters... (Read more)
- 6. Phys. Rev. B 75, 113310 (2007) , “Hole spin polarization in GaAs:Mn/AlAs multiple quantum wells”, V. F. Sapega, O. Brandt, M. Ramsteiner, K. H. Ploog, I. E. Panaiotti, and N. S. AverkievWe study the effect of confinement on the spin polarization of holes bound to Mn acceptors in paramagnetic GaAs:Mn/AlAs multiple quantum wells. It is demonstrated that the polarization of these bound holes is governed by the properties of the host material rather than by quantum confinement. The... (Read more)
- 7. Phys. Rev. B 75, 113201 (2007) , “Local structure around Mn atoms in Si crystals implanted with Mn+ studied using x-ray absorption spectroscopy techniques”, A. Wolska, K. Lawniczak-Jablonska, M. Klepka, M. S. Walczak, and A. MisiukThe local order around Mn atoms in the Mn-implanted Si samples, with ferromagnetic properties, has been investigated by use of x-ray-absorption spectroscopy techniques. Analysis of both extended x-ray-absorption fine structure and x-ray absorption near-edge structure spectra clearly indicates that... (Read more)
- 8. Phys. Rev. B 75, 085203 (2007) , “Structural and magnetic properties of Mn-implanted Si”, Shengqiang Zhou, K. Potzger, Gufei Zhang, A. Mücklich, F. Eichhorn, N. Schell, R. Grötzschel, B. Schmidt, W. Skorupa, M. Helm, J. Fassbender, and D. GeigerStructural and magnetic properties in Mn-implanted, p-type Si were investigated. High resolution structural analysis techniques such as synchrotron x-ray diffraction revealed the formation of MnSi1.7 nanoparticles already in the as-implanted samples. Depending on the Mn fluence,... (Read more)
- 9. Phys. Rev. B 75, 075316 (2007) , “Theoretical investigation of a Mn-doped Si/Ge heterostructure”, J. T. Arantes, Antônio J. R. da Silva, A. Fazzio, and A. AntonelliWe investigate, through ab initio density-functional theory calculations, the electronic and structural properties of neutral Mn impurities at tetrahedral interstitial and substitutional sites in both Si and Ge layers of a Si/Ge heterostructure. We conclude that substitutional Mn at the Ge... (Read more)
- 10. 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)
- 11. Phys. Rev. Lett. 98, 117202 (2007) , “Density-Functional Theory Study of Half-Metallic Heterostructures: Interstitial Mn in Si”, Hua Wu, Peter Kratzer, and Matthias SchefflerUsing density-functional theory within the generalized gradient approximation, we show that Si-based heterostructures with 1/4 layer δ doping of interstitial Mn (Mnint) are half-metallic. For Mnint concentrations of 1/2 or 1 layer, the states induced in the band... (Read more)
- 12. Appl. Phys. Lett. 89, 112122 (2006) , “Enhancement of resistivity of Czochralski silicon by deep level manganese doping”, Kanad Mallik, C. H. de Groot, P. Ashburn, and P. R. WilshawDeep level manganese (Mn) doping has been used to fabricate very high resistivity single crystal silicon substrates grown by the Czochralski method. The Mn has been introduced by ion implantation with a dose of 1014 cm2 of Mn at 100 keV followed by rapid thermal... (Read more)
- 13. Appl. Phys. Lett. 89, 072102 (2006) , “Manganese impurities in boron nitride”, L. V. C. Assali, W. V. M. Machado, and J. F. JustoThe authors carried an ab initio investigation on the properties of Mn impurities in BN, presenting results on stability, spin states, magnetic moment, hyperfine parameters, and formation and transition energies. Substitutional Mn in the cation site in BN was compared to that in GaN and GaAs.... (Read more)
- 14. Appl. Phys. Lett. 89, 012505 (2006) , “Diffusion and clustering of substitutional Mn in (Ga,Mn)As”, Hannes Raebiger, Maria Ganchenkova, and Juhani von BoehmThe Ga vacancy mediated microstructure evolution of (Ga,Mn)As during growth and postgrowth annealing is studied using a multiscale approach. The migration barriers for the Ga vacancies and substitutional Mn together with their interactions are calculated using first principles, and temporal... (Read more)
- 15. J. Appl. Phys. 100, 033717 (2006) , “Magnetic and carrier transport properties of Mn-doped p-type semiconductor LaCuOSe: An investigation of the origin of ferromagnetism”, Hiroshi Yanagi, Shuichi Ohno, Toshio Kamiya, Hidenori Hiramatsu, Masahiro Hirano, and Hideo HosonoLaCuOSe is a wide band gap p-type semiconductor in which high density positive holes can be doped to exhibit degenerate conduction. These features should allow room-temperature ferromagnetism in a dilute magnetic semiconductor (DMS), which follows a theoretical prediction [T. Dietl et al.,... (Read more)
- 16. J. Appl. Phys. 100, 023523 (2006) , “Defects and phase distribution in epitaxial ZnMnSe layers analyzed by transmission electron microscopy”, D. Litvinov, D. Gerthsen, B. Daniel, C. Klingshirn, and M. HetterichOur work is concerned with the occurrence and distribution of the sphalerite, wurtzite, and rocksalt phases, which can be present in the ZnMnSe system, and the analysis of structural defects. For this purpose, ZnMnSe layers with thicknesses between 700 and 1000 nm and Mn concentrations of 0%, 4%,... (Read more)
- 17. J. Appl. Phys. 99, 123515 (2006) , “Raman spectroscopy of (Mn, Co)-codoped ZnO films”, C. L. Du, Z. B. Gu, M. H. Lu, J. Wang, S. T. Zhang, J. Zhao, G. X. Cheng, H. Heng, and Y. F. ChenRaman spectra of (Mn, Co)-codoped ZnO films were investigated as functions of laser line and temperature. It is shown that the Raman shifts for different phonon modes exhibit redshift with temperature increasing, which can be attributed to the anharmonic effect in the material. Strong resonant Raman... (Read more)
- 18. J. Appl. Phys. 99, 103905 (2006) , “Effect of Mn+ ion implantation on the Raman spectra of ZnO”, Hongmei Zhong, Jinbing Wang, Xiaoshuang Chen, Zhifeng Li, Wenlan Xu, and Wei LuRaman measurements have been performed on ZnO bulk materials implanted with 220 keV Mn+ ions with various doses from 1015 to 1017 cm2. The results reveal two modes at about 230 and 523 cm1, respectively, which are not observed in... (Read more)
- 19. J. Appl. Phys. 99, 103502 (2006) , “Correlation of Mn local structure and photoluminescence from CdS:Mn nanoparticles”, Huijuan Zhou, Detlev M. Hofmann, Helder R. Alves, and Bruno K. MeyerThe structure and luminescence properties of Mn2+ in CdS nanoparticles are studied. Electron paramagnetic resonance measurements show the existence of three distinct Mn2+ centers with different local structures in CdS nanocrystals: Mn ions substitutionally incorporated on Cd... (Read more)
- 20. J. Appl. Phys. 99, 073517 (2006) , “Magnetophotoluminescence of Zn0.88Mn0.12Se grown by metal-organic chemical vapor deposition on GaAs substrates”, S. L. Lu, D. S. Jiang, J. M. Dai, C. L. Yang, H. T. He, W. K. Ge, J. N. Wang, K. Chang, J. Y. Zhang, and D. Z. ShenMagnetophotoluminescence properties of Zn0.88Mn0.12Se thin films grown by metal-organic chemical vapor deposition on GaAs substrates are investigated in fields up to 10 T. The linewidth of the excitonic luminescence peaks decreases with the increasing magnetic field (<1 ... (Read more)
- 21. 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)
- 22. Nature 442, 436 (2006) , “Atom-by-atom substitution of Mn in GaAs and visualization of their hole-mediated interactions”, D. Kitchen, A. Richardella, J. -M. Tang, M. E. Flatt, A. YazdaniThe discovery of ferromagnetism in Mn-doped GaAs1 has ignited interest in the development of semiconductor technologies based on electron spin and has led to several proof-of-concept spintronic devices2, 3, 4. A major hurdle for realistic applications of Ga1-XMnXAs, or other dilute magnetic semiconductors, remains that their ferromagnetic transition temperature is below room temperature. Enhancing ferromagnetism in semiconductors requires us to understand the mechanisms for interaction between magnetic dopants, such as Mn, and identify the circumstances in which ferromagnetic interactions are maximized5. Here we describe an atom-by-atom substitution technique using a scanning tunnelling microscope (STM) and apply it to perform a controlled study at the atomic scale of the interactions between isolated Mn acceptors, which are mediated by holes in GaAs. High-resolution STM measurements are used to visualize the GaAs electronic states that participate in the Mn–Mn interaction and to quantify the interaction strengths as a function of relative position and orientation. Our experimental findings, which can be explained using tight-binding model calculations, reveal a strong dependence of ferromagnetic interaction on crystallographic orientation. This anisotropic interaction can potentially be exploited by growing oriented Ga1-XMnXAs structures to enhance the ferromagnetic transition temperature beyond that achieved in randomly doped samples. (Read more)
- 23. Phys. Rev. B 74, 245205 (2006) , “Mn incorporation in as-grown and annealed (Ga,Mn)As layers studied by x-ray diffraction and standing-wave fluorescence”, V. Holý, Z. Matj, O. Pacherová, V. Novák, M. Cukr, K. Olejník, and T. JungwirthA combination of high-resolution x-ray diffraction and a technique of x-ray standing-wave fluorescence at grazing incidence is employed to study the structure of a (Ga,Mn)As-diluted magnetic semiconductor and its changes during post-growth annealing steps. We find that the film is formed by a... (Read more)
- 24. Phys. Rev. B 74, 241303(R) (2006) , “Enhancement of interactions between magnetic ions in semiconductors due to declustering”, A. Franceschetti, S. V. Barabash, J. Osorio-Guillen, A. Zunger, and M. van SchilfgaardeIt is often assumed that the exchange interaction between two magnetic ions in a semiconductor host depends only on the distance and orientation of the magnetic ions. Using first-principles electronic structure calculations of Mn impurities in GaAs, we show that the exchange interaction between two... (Read more)
- 25. Phys. Rev. B 74, 235213 (2006) , “Mn 3d electronic configurations in (Ga1−xMnx)As ferromagnetic semiconductors and their influence on magnetic ordering”, F. Kronast, R. Ovsyannikov, A. Vollmer, H. A. Dürr, W. Eberhardt, P. Imperia, D. Schmitz, G. M. Schott, C. Ruester, C. Gould, G. Schmidt, K. Brunner, M. Sawicki, and L. W. MolenkampWe applied x-ray absorption spectroscopy and x-ray magnetic circular dichroism (XMCD) at the Mn 2p-3d resonances to study the Mn 3d electronic configuration and the coupling of Mn 3d magnetic moments in various Ga1−xMnxAs films.... (Read more)
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