UB Heads $10 Million DARPA Research Project to Develop New Materials for Field of "Spintronics"

Electrons could take on new functions in "quantum computers"

Release Date: September 13, 2000

BUFFALO, N.Y -- The University at Buffalo is the lead institution in a $10 million project to develop specific ferromagnetic materials for use in "spintronics," the emerging research field in physics focused on spin-dependent phenomena applied to electronic devices.

The U.S. Defense Advanced Research Projects Agency (DARPA) will fund the nine-institution consortium project, which focuses on esoteric semiconductor nanostructure research.

The promise of spintronics is based on manipulation not only of the charge of electrons, but also their spin, which enables them to perform new functions. The ability to manage electron spin is expected to lead to the development of remarkable improvements in electronic systems and devices used in photonics, data processing and communications technology.

These effects can be exploited, however, only through the development of radically new materials and technologies, specifically magnetic semiconductors and structures that will permit scientists to manipulate the direction of the electron spin. DARPA is one of the principal sources of funding for research in the development of these technologies.

The goal of the UB project is to produce new magnetic semiconductors and prototype devices through the cooperative work of seven interdisciplinary teams at nine institutions. The effort will be directed and coordinated by scientists in UB's Center for Advanced Photonic and Electronic Materials (CAPEM), led by principal investigator Bruce D. McCombe, director and professor of physics.

All over the world, "spin doctors" are working to understand the characteristics of spin-dependent phenomena in order to develop a new generation of electronic-spintronic devices.

Professors Hong Luo, Athos Petrou and McCombe in the Department of Physics in the UB College of Arts and Sciences have been extensively involved in research on properties of spins in magnetic semiconductors and the materials that are specifically involved in this project. Their work puts UB in the forefront of this research field.

In addition to UB, the participating institutions involved in the project are the University of Notre Dame, the University of Wuerzburg (Germany), Indiana University, the University of Texas at Austin, the U.S. Naval Research Laboratory (NRL), North Carolina State University, Vanderbilt University and Worcester Polytechnic Institute.

Each institutional team represents expertise and capabilities in areas ranging from basic theory to fabrication for which their institutional capabilities are particularly well-suited. The co-investigators representing the institutions are Hong Luo (UB), Jacek K. Furdyna (Notre Dame), Norman H. Tolk (Vanderbilt), Laurens W. Molenkamp (Wurtzburg), Jerry R. Meyer (NRL), Allan H. MacDonald (Indiana) and Ki Wook Kim (NCSU).

UB's Luo explains that spintronics aims to exploit one of the subtle quantum properties of the electron -- its spin -- to yield a desired outcome.

"Electrons carry an intrinsic electric charge," he points out, "and most electronic and optical devices (i.e. lasers, detectors of optical radiation, etc.) operate by manipulating these charges through the use of electric voltages.

"Spin is another important intrinsic property of electrons," Luo says. "Like all things that spin, electrons spin in a direction usually defined by the axis of the motion. In the case of an electron, spin can take only one of two positions with regard to some arbitrarily chosen direction -- spin-up or spin-down."

Conventional electronic devices use only the electron's charge. In them, spinning electrons point randomly in all directions and are not directly involved in device function. Spintronic devices, however, Luo says, aim to take advantage of both properties.

According to Luo, if spin can be manipulated, electrons will be able to perform new functions in data processing and storage. In fact, data processing and storage could be merged in the same basic component.

This would make it possible to produce, among other things, "quantum computers" that would not have to relay on binary digits (1 or 0) but could encode information in different spin states -- up, down or any of an infinite number of possibilities involving a mixture of both.

"The consequence," Luo says, "will be a fundamental change in the concept of electronic device design resulting not only in higher computing speed, but in great improvements in such fields as photonics and data transmission and communication."

In order to align or otherwise manipulate the orientation of spin, however, structures of metals or semiconductors must be developed that are capable of sensing electron spin direction and, based on this information, creating gateways for electrons. Such materials might allow spins pointing in one direction to pass, for instance, while spins pointing in the opposite direction might be turned away.

McCombe explains that the UB project aims to develop magnetic conducting materials -- specifically those made of ferromagnetic heterostructures {In(Mn)As/Ga(Mn)Sb/A1(Mn)Sb} -- and novel devices from these materials. This group of materials has great potential for electronic devices and for optical devices to produce and detect infrared and far infrared signals (useful for, e.g., heat sensing and night vision).

"The funding to the UB consortium represents roughly 10 percent of the presently projected funding in this DARPA program," McCombe says. "Other agencies, such as the National Science Foundation, have recently begun to put substantial amounts of research funding into this new area."

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