Enhanced half-metallicity in carbon-chain–linked trigonal graphene

• How to enhance the half-metallicity for a trigonal graphene is studied.
• The spin polarization is only changed slightly if even-numbered carbon atom chains are linked.
• It shows a prominent half-metallicity if odd-numbered carbon atom chains are linked.

The spin polarization property of a zigzag-edge trigonal graphene (ZTG) linked with different-length carbon chains Cn is investigated theoretically. It has been found that the enhancement of such a property completely depends on that the number of carbon atoms in a chain being odd or even. If it is an even number, the spin polarization is only changed slightly due to the nearly nonmagnetic property of these carbon chains. In contrast, while it is an odd number, the spin polarization is enhanced significantly to a larger energy range, i.e., showing a prominent half-metallicity and perfect spin-filter effects, owing to interactions of the ZTG and carbon chains with the strong ferromagnetism property. Deepgoing analyses show that these results are intimately related to a polyyne-like configuration for carbon chains in nanojunctions and the transition from the bipolar magnetic semiconductor to half-metallicity. Our findings suggest that this simple structure might promise importantly potential applications for developing nano-scale spintronics devices.

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