October 2012

Researchers developed a new technique called HARPES (Hard x-ray Angle-Resolved PhotoEmission Spectroscopy) that can be used to investigate the bulk electronic structure of different materials. In the first application, they checked the bulk electronic structure of the prototypical dilute magnetic semiconductor gallium manganese arsenide, and discovered that the material’s ferromagnetism arises from both of the two different mechanisms that have been proposed to explain it. Understanding the source of ferromagnetism in dilute magnetic semiconductors is an important milestone toward using these materials in Spintronics devices.

HARPES, which is based on the photoelectric effect, enables scientists to study bulk electronic effects with minimum interference from surface reactions or contamination. It also allows them to probe buried layers and interfaces that are ubiquitous in nanoscale devices, and are key to smaller logic elements in electronics, novel memory architectures in spintronics, and more efficient energy conversion in photovoltaic cells.

Researchers from the US Naval Research Laboratory (NRL) discovered a way to use graphene as an extremely thin "tunnel barrier" to conduction. This could be very useful for Spintronics devices. The researchers have shown that graphene can serve as an excellent tunnel barrier when current is directed perpendicular to the plane of carbon atoms. The spin polarization of the current is also preserved by the tunnel barrier.

The researchers replaced the normally used oxide barriers (which introduce defects into the system and feature too high a resistance) with graphene - which is defect resistant and chemically inert and stable.