Voltage-controlled spin injection with an endohedral fullerene [email protected] dimer

Appl. Phys. Lett. 102, 173101 (2013).

Alireza Saffarzadeh, George Kirczenow.

Department of Physics, Payame Noor University, P.O. Box 19395-3697 Tehran, Iran and

Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.



Spin-dependent transport through an endohedral fullerene [email protected]60 dimer with gold electrodesis explored theoretically using density functional and extended Hückel theory. Density of statesspin polarizations up to 95%, due to spin-splitting of Co 3d orbitals, are found by varying the gate and/or bias voltage. The current-voltage characteristics and strong (up to 100%) spinpolarization of the current indicate that the device can be utilized for highly efficient spin injection into nonmagnetic conductors. This finding opens the way to the realization of electrostatically tuned spintronic nano devices less than 2 nm in size, without ferromagnetic electrodes.

© 2013 AIP Publishing LLC

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Carbon-based nanostructures such as fullerenes, carbon nanotubes, and graphene, are promising candidates for spintronic applications because of their weak spin-orbit coupling and hyperfine interaction which lead to long spin coherence lengths. In particular, a fullerene C60 molecule is an interesting carbon nanostructure that can be used as a molecular bridge in magnetic tunnel junctions due to its remarkable structural stability and electronic properties that make the molecule convenient for easier spin injection in magnetic nanojunctions. The present paper explores the spintronic properties of a dimer consisting of two C60 Buckminster fullerene molecules, each containing an encapsulated cobalt atom. The dimer is sandwiched between two non-magnetic gold electrodes. For suitable gate and bias voltages we predict this nanostructure to exhibit density of states spin polarizations as large as 95%, due to the spin-splitting of the Co 3d orbitals. We find this strong spin polarization to give rise to efficient spin filtering of electric currents passing from one gold electrode to the other through the dimer, i.e., up to 100% spin polarization of the current injected into the downstream non-magnetic electrode. This spin polarization of the injected current can be switched on and off by varying gate and bias voltages. This electrostatic activation should lend itself to integration of such nano spin injectors with conventional nano electronic devices. Also, since magnetic electrodes are not required to achieve spin injection in this novel way, the size of the device required for spin injection is that of the [email protected]60 dimer itself, i.e., less than 2 nanometers. Therefore as well as being of fundamental interest, systematic experimental studies of encapsulated magnetic atoms in the fullerene dimer based on these findings may be relevant for nanoelectronic and spintronic applications.


Voltage-controlled spin injection with an endohedral fullerene Co@C60 dimer



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