Spin transport in carbon nanotubes with magnetic vacancy-defects

Zeila Zanolli and J.-C. Charlier

Phys. Rev. B 81, 165406 – Published 2 April 2010

Abstract

The spin-polarized electron transport properties of metallic carbon nanotubes containing vacancies are investigated using first-principles and nonequilibrium Green’s function techniques. Reconstructed mono- and trivacancies, containing carbon atoms with unsaturated bonds, behave like quasilocalized magnetic impurities. However, in conventional ab initio simulations, these magnetic defects are artificially repeated periodically (supercell method) and are thus incorrectly coupled by long range interactions. Consequently, a technique based on an open system with an isolated magnetic impurity is used here to accurately describe the local magnetic properties of these defects, revealing spin-dependent conductances in tubes, which could be exploited in spintronic nanodevices.

Received 11 January 2010

DOI:https://doi.org/10.1103/PhysRevB.81.165406

Authors & Affiliations

Zeila Zanolli and J.-C. Charlier

Institute of Condensed Matter and Nanosciences–Nanophysics (IMCN/NAPS), European Theoretical Spectroscopy Facility (ETSF), Université catholique de Louvain, Place Croix du Sud 1 (Boltzmann), 1348 Louvain-la-Neuve, Belgium

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Issue

Vol. 81, Iss. 16 — 15 April 2010

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Images

Figure 1
(Color online) Ball-and-stick models illustrating fully ab initio optimized atomic structures of a (5,5) CNT containing a reconstructed monovacancy (a, b), divacancy (c, d), and trivacancy (e, f) in various topological orientations (tilted and parallel, as defined in the text). The most stable structure for each defect type is labeled as ground state (g.s.). The newly formed carbon bonds (red sticks) and the dangling carbon atoms (red balls) are indicated by $l$ and $C_{D}$ , respectively.Reuse & Permissions
Figure 2
(Color online) Total magnetization $(μ_{B})$ for the $1 \times 1 \times n$ supercell containing one monovacancy calculated within the PBC scheme (red curve ◼—◼) and for the open system with $1 \times 1 \times n$ core region (black curve ●—●). Indirect Exchange coupling ( $J$ , meV) for the $1 \times 1 \times 2 n$ supercell containing two monovacancies at distance $n d_{0}$ (blue curve ▲—▲). All the calculations are performed on a (5,5) CNT containing a monovacancy reconstructed in the tilted configuration, as illustrated in the inset.Reuse & Permissions
Figure 3
(Color online) From top to bottom, spin-polarized electronic conductances of the (5,5) CNT with mono-, di-, and trivacancy in the tilted (left column) and parallel (right column) configurations. The corresponding optimized atomic structures are illustrated in insets. The magnetization, calculated within the open-system scheme, is also reported. The conductance of the pristine (5,5) tube is indicated by a dashed line. Red and black curves correspond to majority and minority spin channels, respectively.Reuse & Permissions
Figure 4
(Color online) DoS calculated within the NEFG formalism for the (5,5) CNT containing a monovacancy reconstructed in its most stable (c) and next stable (d) configurations. The DoS allows to identify the degree of localization of the dips in the transmission curve (indicated by arrows), also reported in the figure [(a) and (b)] to facilitate the comparison. Red and black curves correspond to majority and minority spin channels, respectively. Wave functions illustrate the degree of localization of these electronic states. The tilted vacancy induces a more extended state (e) than the parallel one (f).Reuse & Permissions
Figure 5
(Color online) Quantum electron conductance and total magnetic moment for the (10,10) CNT containing a reconstructed monovacancy relaxed using the SZ (a) and the DZ (b) quality basis set. The magnetic moment is calculated using the open-system scheme. Red and black curves in (b) correspond to majority and minority spin channels, respectively.Reuse & Permissions

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