Inverse magnetoresistance of molecular junctions

Dalgleish, Hugh; Kirczenow, George

doi:10.1103/physrevb.72.184407

Cited by 58 publications

(58 citation statements)

References 31 publications

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“…To couple the extended molecule to the electron reservoirs, as in previous work [14][15][16][19][20][21][22][23][24][25], we attach a large number of semi-infinite quasi-one-dimensional ideal leads to the valence orbitals of the outer gold atoms of the extended molecule. We find the transmission amplitudes t ji by solving the Lippmann-Schwinger equation…”

Section: Conductance Calculationsmentioning

confidence: 99%

Mechanism of the enhanced conductance of a molecular junction under tensile stress

2014

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Despite its fundamental importance for nano physics and chemistry and potential device applications, the relationship between atomic structure and electronic transport in molecular nanostructures is not well understood. Thus the experimentally observed increase of the conductance of some molecular nano junctions when they are stretched continues to be counterintuitive and controversial. Here we explore this phenomenon in propanedithiolate molecules bridging gold electrodes by means of ab initio computations and semi-empirical modeling. We show that in this system it is due to changes in Au-S-C bond angles and strains in the gold electrodes, rather than to the previously proposed mechanisms of Au-S bond stretching and an associated energy shift of the highest occupied molecular orbital and/or Au atomic chain formation. Our findings indicate that conductance enhancement in response to the application of tensile stress should be a generic property of molecular junctions in which the molecule is thiol-bonded in a similar way to gold electrodes.

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Section: Conductance Calculationsmentioning

confidence: 99%

Mechanism of the enhanced conductance of a molecular junction under tensile stress

2014

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“…In the first implementations based on density functional theory, the electrodes were treated as jellium which were coupled to the scattering region. 15,17,18 Large systems up to devices can be described using semiempirical tight-binding methods for the electronic structure, 13,14,19,29,30 while approaches using DFT for both the description of the electrodes via self-energies and the scattering region promise the highest accuracy. 27,28,[31][32][33][34][35][36][37][38][39][40][41][42][43][44] Among these implementations, various DFT methods have been applied.…”

Section: Fig 1 (Color Online)mentioning

confidence: 99%

“…Given a FLEUR electronic-structure calculation, it is necessary to construct these parts of the Hamiltonian from the resulting WFs hopping elements [Eq. (19)]. We focus on the correct treatment of the scattering region (see Fig.…”

Section: Construction Of the Hamiltonian In Real Spacementioning

confidence: 99%

One-dimensional ballistic transport with FLAPW Wannier functions

et al. 2012

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We present an implementation of the ballistic Landauer-Büttiker transport scheme in one-dimensional systems based on density functional theory calculations within the full-potential linearized augmented plane-wave (FLAPW) method. In order to calculate the conductance within the Green's function method, we map the electronic structure from the extended states of the FLAPW calculation to Wannier functions, which constitute a minimal localized basis set. Our approach benefits from the high accuracy of the underlying FLAPW calculations, allowing us to address the complex interplay of structure, magnetism, and spin-orbit coupling and is ideally suited to study spin-dependent electronic transport in one-dimensional magnetic nanostructures. To illustrate our approach, we study ballistic electron transport in nonmagnetic Pt monowires with a single stretched bond including spin-orbit coupling, and in ferromagnetic Co monowires with different collinear magnetic alignment of the electrodes with the purpose of analyzing the magnetoresistance when going from tunneling to the contact regime. We further investigate spin-orbit scattering due to an impurity atom. We consider two configurations: a Co atom in a Pt monowire and vice versa. In both cases, the spin-orbit induced band mixing leads to a change of the conductance upon switching the magnetization direction from along the chain axis to perpendicular to it. The main contribution stems from ballistic spin scattering for the magnetic Co impurity in the nonmagnetic Pt monowire, and for the Pt scatterer in the magnetic Co monowire from the band formed from states with d xy and d x 2 −y 2 orbital symmetry. We quantify this effect by calculating the ballistic anisotropic magnetoresistance, which displays values up to as much as 7% for ballistic spin scattering and gigantic values of around 100% for the Pt impurity in the Co wire. In addition, we show that the presence of a scatterer can reduce as well as increase the ballistic anisotropic magnetoresistance.

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“…Fundamental spin-dependent electron transport properties have been demonstrated in the context of molecular spintronics [15][16][17][18][19][20] which is a promising field of research in basic science and potential applications. Even the ultimately thin wires made of single atomic chains are produced under experimental conditions and are actively studied.…”

Section: Introductionmentioning

confidence: 99%

Spintronic properties of carbon-based one-dimensional molecular structures

et al. 2006

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In this paper we present an extensive study of the electronic, magnetic, and transport properties of finite and infinite periodic atomic chains composed of carbon atoms and 3d transition metal ͑TM͒ atoms using firstprinciples methods. Finite-size, linear molecules made of carbon atomic chains caped with TM atoms, i.e., TM-C n -TM structures are stable and exhibit interesting magnetoresistive properties. The indirect exchange interaction of the two TM atoms through a spacer of n carbon atoms determines the type of the magnetic ground state of these structures. The n-dependent ͑n = 1 to 7͒ variations of the ground state between ferromagnetic and antiferromagnetic spin configurations exhibit several distinct forms, including regular alternations for Ti, V, Mn, Cr, Fe, and Co, and irregular forms for Sc and Ni cases. We present a simple analytical model that can successfully simulate these variations, and the induced magnetic moments on the carbon atoms. Depending on the relative strengths of the carbon s, p and TM d orbital spin-dependent coupling and on the on-site energies of the TM atoms there induces long-range spin polarizations on the carbon atoms which mediate the exchange interaction. While periodically repeated TM-C n atomic chains exhibit half-metallic properties with perfect spin polarization at the Fermi level, finite but asymmetric chains comprising single, double, and triple TM atoms display interesting spin-dependent features. These properties may be altered when these structures are coupled to electrodes. However, when connected to appropriate electrodes the TM-C n -TM atomic chains act as molecular spin valves in their ferromagnetic states due to the large ratios of the conductance values for each spin type.

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Inverse magnetoresistance of molecular junctions

Cited by 58 publications

References 31 publications

Mechanism of the enhanced conductance of a molecular junction under tensile stress

Mechanism of the enhanced conductance of a molecular junction under tensile stress

One-dimensional ballistic transport with FLAPW Wannier functions

Spintronic properties of carbon-based one-dimensional molecular structures

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