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Proceedings ArticleDOI

Magnetic cages of GaN nanoclusters doped with Gd and Nd

11 Feb 2010-Vol. 7602, pp 64-70
TL;DR: In this article, the authors reported results of ab initio calculations on (GaN)n nanoclusters with n = 12, 16, 22, and 24 using generalized gradient approximation (GGA) for the exchange-correlation
Abstract: We report results of ab initio calculations on (GaN)n nanoclusters with n = 12, 16, 22, and 24 using generalized gradient approximation (GGA) for the exchange-correlation energy. We find cage structures of GaN clusters to be lower in energy as compared to bulk fragments which have been fully optimized. Selected cages have been doped with Gd and Nd atoms by substituting Gd and Nd on Ga sites, respectively. The atomic structures of such doped nanoclusters have been optimized using spin-polarized GGA and by including all f electrons on the rare earth atoms. We find the doped nanoclusters to be magnetic with 7 μ B (3 μ B ) magnetic moments when 1 Gd (Nd) atom is doped. When 2 Gd (Nd) atoms are substituted on different Ga sites, there is often a ferromagnetic coupling between the rare earth atoms, but we also find zero net magnetic moment in the nanocluster depending upon the separation between the doped atoms suggesting that both ferromagnetic and antiferromagnetic couplings may occur between the rare earth dopants.
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Book ChapterDOI
01 Jan 2016
TL;DR: In this paper, the atomic structure and magnetic properties of GaN doped with selected rare earth atoms were investigated and the effects of codoping these materials with Si are also discussed, and it has been found that the doping of a Eu atom on a Ga site in bulk GaN creates significant local deformation and it costs 1.84 eV.
Abstract: Results of ab initio pseudopotential calculations are presented concerning the atomic structure and magnetic properties of GaN doped with selected rare earth atoms. Effects of codoping these materials with Si are also discussed. It has been found that the doping of a Eu atom on a Ga site in bulk GaN creates significant local deformation and it costs 1.84 eV. However, the addition of a Si atom makes Eu doping in bulk GaN energetically favorable as strain from an oversized Eu atom and an undersized Si atom is compensated. Therefore codoping of Si facilitates doping of rare earths in GaN. The excess charge due to codoping of Si tends to cause Eu to be in a 2+ state and the magnetic moment on Eu ion is enhanced to 7 μB. Further studies have shown that Eu atoms tend to cluster with interatomic separation of about 5 A and there is ferromagnetic coupling. For rare earth atoms in nanoparticles, ab initio calculations have been performed on (GaN)n (n = 12, 16, 22, and 32) nanoclusters with Eu, Gd, and Nd atoms substituting on Ga sites. These studies have yielded preferred atomic structures and magnetic behavior. Cage structures of these GaN nanoclusters were found to be lower in energy as compared to bulk fragments. Specific results show that Eu-doping in GaN nanoparticles is favorable compared with bulk GaN since a large fraction of atoms in a nanocluster lie on the surface where strain can be lower. Codoping of Si further facilitates Eu doping as in the case of bulk GaN.

3 citations

Journal ArticleDOI
TL;DR: In this paper, the magnetic moments are localized on the Eu site with a large value of 6μB (7μB) in all cases of Eu (Eu+Si) doping.
Abstract: Ab initio calculations on Eu doped (GaN)n (n = 12, 13, and 32) nanoparticles show that Eu doping in nanoparticles is favorable compared with bulk GaN as a large fraction of atoms lie on the surface where strain can be released compared with bulk where often Eu doping is associated with a N vacancy. Co-doping of Si further facilitates Eu doping as strain from an oversized Eu atom and an undersized Si atom is compensated. These results along with low symmetry sites in nanoparticles make them attractive for developing strongly luminescent nanomaterials. The atomic and electronic structures are discussed using generalized gradient approximation (GGA) for the exchange-correlation energy as well as GGA + U formalism. In all cases of Eu (Eu + Si) doping, the magnetic moments are localized on the Eu site with a large value of 6μB (7μB). Our results suggest that co-doping can be a very useful way to achieve rare-earth doping in different hosts for optoelectronic materials.

3 citations