Magneto-resistance of organic spin valves due to spin-polarized tunnel injection and extraction of charge carriers

The quantum Hall effect, observed in a two-dimensional (2D) electron gas subjected to a perpendicular magnetic field, imposes a 1D-like chiral, downstream, transport of charge carriers along the sample edges. Although this picture remains valid for electrons and Laughlin’s fractional quasiparticles, it no longer holds for quasiparticles in the so-called hole-conjugate states. These states are expected, when disorder and interactions are weak, to harbor upstream charge modes. However, so far, charge currents were observed to flow exclusively downstream in the quantum Hall regime. Studying the canonical spin-polarized and spin-unpolarized v = 2/3 hole-like states in GaAs-AlGaAs heterostructures, we observed a significant upstream charge current at short propagation distances in the spin unpolarized state.

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Spin-polarized transport in magnetically assembled carbon nanotube spin valves

Applied Physics Letters ◽

10.1063/1.2221910 ◽

2006 ◽

Vol 89 (3) ◽

pp. 033119 ◽

Cited By ~ 20

Author(s):

R. Thamankar ◽

S. Niyogi ◽

B. Y. Yoo ◽

Y. W. Rheem ◽

N. V. Myung ◽

...

Keyword(s):

Carbon Nanotube ◽

Spin Valves ◽

Spin Polarized ◽

Polarized Transport ◽

Spin Polarized Transport

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Theoretical Study of Spin Conduction in the Ni/DTE/Ni Nanohybrid

Nano Hybrids ◽

10.4028/www.scientific.net/nh.4.1 ◽

2013 ◽

Vol 4 ◽

pp. 1-20 ◽

Cited By ~ 1

Author(s):

Kanchan Ulman ◽

Mighfar Imam ◽

Shobhana Narasimhan ◽

Anders Odell ◽

Anna Delin

Keyword(s):

Density Functional ◽

Transmission Function ◽

Spin Current ◽

Functional Theory ◽

Contact Materials ◽

Spin Polarized ◽

Interesting Candidate ◽

High Bias ◽

Conductance Ratio ◽

Magneto Resistance

The photoswitching molecule dithienylethene (DTE) is an interesting candidate for constructing optoelectronic molecular devices since it can be made to switch between a closed and an open conformation using light. We here report computations, based on density functional theory (DFT) and the non-equilibrium Green function (NEGF) method, of the spin-resolved conductance of the two DTE isomers attached to spin-polarized nickel leads. Results are compared and contrasted to those of other contact materials (nonmagnetic Ni, Ag, and Au), analyzing the physical origins of the various features in the transmission function. It was found rather surprisingly, that the two spin channels in the Ni/DTE/Ni device have almost identical I-V characteristics, despite one channel being d-dominated and the other one s-dominated. It was also observed that the Ni-based device exhibits a sustained high conductance ratio also for high bias - a property that may be of relevance in future device design. Furthermore, two computational schemes for calculating the conductance were compared and analyzed. It was found that even for very small bias the molecular orbital polarization was decisive for spin-related properties such as the spin current ratio and magneto-resistance in the Ni/DTE/Ni device.

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