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New Hybrid Material for Future Spin Transistors

Jülich, 10 January 2017 – Spin-based transistors may replace conventional transistors in future since they require considerably less energy, however their industrial implementation has so far been hampered due to the lack of a suitable material. Early-career researcher Zeila Zanolli has now discovered a novel combination of graphene and barium manganese oxide which satisfies the conflicting requirements. Simulations conducted on the supercomputers at the Jülich Supercomputing Centre (JSC) have shown that the new hybrid material permits both precise spin orientation and good spin transport.

Transistors are arguably the most important basic components of current storage sticks and processors. Up to several billion of them are contained in current computer chips. The most common types of transistors make use of only the electric charge of electrons to switch from one state to the other. In spin-based transistors, instead, the switching processes are based on changes in the electron spin. This is a general feature for “spintronic” devices and their applications. The energy required for switching spins would be a whole order of magnitude lower than what is needed for switching conventional transistors, resulting in enormous energy savings.

Practical implementation of spin transistors, however, is complicated by opposing material requirements. Traditional semiconductors, as currently used in the production of chips, are characterized by a strong spin–orbit coupling. Hence, in these materials the electron spins can be easily oriented by means of an external field. Such targeted spin polarization, however, only ranges across extremely short distances and cannot be maintained long enough to subsequently manipulate the spins. In novel carbon-based semiconductors such as carbon nanotubes or graphene, the spin polarization remains intact over longer distances, but it is almost impossible to control it from the outside because of the weak spin-orbit coupling of Carbon.

However, the advantages of the two material classes complement each other if graphene is combined with a magnetic semiconductor. Early-career scientist Zeila Zanolli was able to verify this remarkable property as part of her Marie Curie Fellowship position at Forschungszentrum Jülich’s Peter Grünberg Institute (PGI-1). The Jülich supercomputers JUQUEEN and JURECA – which are among the fastest in Europe – were used for the compute-intensive analysis. Zanolli, who now heads the DFG young investigators group on Nanospintronics at RWTH Aachen University, used the computer simulations to show that the newly created material combination “inherits” the long spin diffusion length of the graphene, while the interaction is so strong that the polarization of the electron spin is transferred to the graphene by the manganese atoms.

Original publication:

Graphene-multiferroic interfaces for spintronics applications
Zeila Zanolli
Scientific Reports 6, Article number: 31346 (Published online: 23 August 2016)

Further information:

Peter Grünberg Institute, Quantum Theory of Materials (PGI-1/IAS-1)

Nanospintronics Group, RWTH Aachen