Manipulation of half-metallicity and ferromagnetism in N-doped CdS nanowire
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RESEARCH PAPER
Manipulation of half-metallicity and ferromagnetism in N-doped CdS nanowire Fu-bao Zheng • Chang-wen Zhang Shi-shen Yan • Feng Li
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Received: 17 November 2012 / Accepted: 11 April 2013 / Published online: 24 April 2013 Ó Springer Science+Business Media Dordrecht 2013
Abstract The spin-polarization and magnetic coupling of N-doped CdS nanowires (NWs) with a ´˚ diameter size of 12.33 A have been investigated through first-principles calculations. The doped N prefers surface S sites and leads to a half-metallic property. The magnetic interaction between the nearest and the next-nearest N dopants results in a strong ferromagnetic (FM) coupling, while, when the dis˚´ , the tance between N dopants is larger than 8.0 A ground state of the system tends to be paramagnetic. Also, a nitrogen concentration threshold to produce the FM order is estimated to be 8.3 %. The results of incorporation of N dopants to CdS NWs pave a promising way to realize potential applications in spintronics. Keywords First-principles calculations CdS nanowire Ferromagnetism
F. Zheng C. Zhang (&) F. Li School of Physics and Technology, University of Jinan, Jinan 250022, Shandong, People’s Republic of China e-mail: [email protected] S. Yan School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, Shandong, People’s Republic of China
Diluted magnetic semiconductors (DMSs) have attracted great attention owning to their fundamental physics and promising applications in spintronics (Awschalom and Flatte´ 2007; Song et al. 2006), because of the possibility that their spin and charge can be manipulated. However, no convincing evidence can verify that the ferromagnetic (FM) order in transition-metal (TM)-doped DMSs is intrinsic (Coey and Chamber 2008), because of the presence of TM magnetic precipitate in forms of clusters detrimental to the real applications (Kim et al. 2003). With respect to TM-doped DMSs, unexpected room-temperature (RT) ferromagnetism that is free of TM species has recently been reported in 2p light elements-doped ZnO (Pan et al. 2007), ZnS (Zhang et al. 2010), SnO2 (Zhang and Yan 2009), TiO2 (Yang et al. 2008), and MgO (Slipukhina et al. 2011), which is nowadays referred as sp/d0 magnetism. Shortly after, the RT ferromagnetism in these 2p light elements-doped DMSs was confirmed by some experiments (Wen et al. 2009; Bao et al. 2011; Hong et al. 2011; Tan et al. 2011). These kinds of sp/d0 FM properties are very intriguing because they challenge the traditional understanding of the physical mechanism in DMSs. As one of the most important group II–VI semiconductor, CdS NW has recently been synthesized by using a chemical solution process (Wang et al. 2006, 2007), and then its physical properties were discussed by Lin et al. (2008). The synthesis of CdS NW opens up possibilities for realizing RT ferromagnetism, because of its lower mass density, and very large
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surface-to-weight ratio. In fact, RT p-electron-induced sp/d0 ferromagnetism in bulk CdS has bee
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