Magnetics Business & Technology - Winter 2012 - (Page 4)

EDITOR’S CHOICE Spintronic technology, in which data is processed on the basis of electron “spin” rather than charge, promises to revolutionize the computing industry with smaller, faster and more energy efficient data storage and processing. Materials drawing a lot of attention for spintronic applications are dilute magnetic semiconductors – normal semiconductors to which a small amount of magnetic atoms is added to make them ferromagnetic. Understanding the source of ferromagnetism in dilute magnetic semiconductors has been a major road-block impeding their further development and use in spintronics. Now a significant step to removing this roadblock has been taken. A multi-institutional collaboration of researchers led by scientists at the US Department of Energy’s Lawrence Berkeley National Laboratory, using a new technique called HARPES, for Hard x-ray Angle-Resolved PhotoEmission Spectroscopy, has investigated the bulk electronic structure of the prototypical dilute magnetic semiconductor gallium manganese arsenide. Their findings show that the material’s ferromagnetism arises Alexander Gray (left) and Charles from both of the two different Fadley at Beamline 9.3.1 of Berkemechanisms that have been ley Lab’s Advanced Light Source where they are now carrying out proposed to explain it. HARPES experiments. (Photo by “This study represents the Roy Kaltschmidt, Berkeley Lab) first application of HARPES to a forefront problem in materials science, uncovering the origin of the ferromagnetism in the so-called dilute magnetic semiconductors,” said Charles Fadley, the physicist who led the development of HARPES. “Our results also suggest that the HARPES technique should be broadly applicable to many new classes of materials in the future.” For the semiconductors used in today’s computers, tablets and smart phones, once a device is fabricated it is the electronic structures below the surface, in the bulk of the material or in buried layers, that determine its effectiveness. HARPES, which is based on the photoelectric effect described in 1905 by Albert Einstein, 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. “The key to probing the bulk electronic structure is using hard x-rays, which are x-rays with sufficiently high photon energies to eject photoelectrons from deep beneath the surface of a solid material,” said Gray, who worked with Fadley to develop the HARPES technique. “High-energy photons impart high kinetic energies to the ejected photoelectrons, enabling them to travel Another Advance on the Road to Spintronics longer distances within the solid. The result is that more of the signal originating from the bulk will be detected by the analyzer.” In this new study, Gray and Fadley and their collaborators, used HARPES to shed important new light on the electronic bulk structure of gallium manganese arsenide (GaMnAs). As a semiconductor, gallium arsenide is second only to silicon in widespread use and importance. If a few percent of the gallium atoms in this semiconductor are replaced with atoms of manganese the result is a dilute magnetic semiconductor. Such materials would be well-suited for further development into spintronic devices if the mechanisms behind their ferromagnetism were better understood. “Our bulk-sensitive HARPES measurements revealed that the manganese-induced impurity band is located mostly between the gallium arsenide valence-band maximum and the Fermi level, but the manganese states are also merged with the gallium arsenide valence bands,” Gray said. “This is evidence that the two mechanisms co-exist and both act to give rise to ferromagnetism.” Follow Us QUAN: Could Robotics Be the Cure For Cancer? As Quantum International Corp. explores the potential of tiny nanobots to revolutionize medicine, new robotics breakthroughs could soon pave the way for a potential cure for cancer. Scientists at the NanoRobotics Laboratory at Canada’s École Polytechnique de Montréal have discovered a way to wirelessly steer tiny robots and other objects through the blood vessels of living creatures using the magnetic coils in MRI machines. These microbots can travel deep inside the body, visiting places that catheters can’t go and performing tasks previously impossible without invasive surgery. While the tech isn’t quite ready for human testing yet, one of the first medical applications for these microscopic machines could be treating cancers. “Using robots to deliver cancer-killing medicine directly to a tumor deep within the body could forever change the treatment of the disease,” said Quantum CEO Robert Federowicz. “The market for such astonishing technology would obviously be enormous. Quantum is dedicated to bringing just such innovations out of the laboratory and into the global marketplace.” In fact, Quantum is already working to leverage demand for powerful new medical technologies. The company is close to an agreement with Poland’s Industrial Research Institute for Automation and Measurement (PIAP) to assist in the commercialization of the Resuscitator, a portable device designed to ensure that chest compressions, the element of CPR most prone to human error, can be easily administered by amateurs and professionals alike. Quantum is working to develop the next generation of robotics technology to compete in a booming global industry alongside Intuitive Surgical, Inc., iRobot Corp. and Dover Corp. 4 Magnetics Business & Technology • Winter 2012 www.MagneticsMagazine.com http://www.MagneticsMagazine.com

Table of Contents for the Digital Edition of Magnetics Business & Technology - Winter 2012

Magnetics Business & Technology - Winter 2012
Editor's Choice
Permanent Magnet Industry Outlook - 2013
Magnet Materials and Their Properties
Magnets • Materials • Measurement
Application • Component Developments
Magnetics 2013: Conference Preview
Research & Development
2012 Resource Guide
Industry News
Marketplace
Advertising Index
Spontaneous Thoughts: Retired, Senile and Dead

Magnetics Business & Technology - Winter 2012

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