Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Prediction of Intrinsic Magnetism at Silicon Surfaces Could Lead to Single-Spin Magnetoelectronics

27.08.2010
The integration of single-spin magnetoelectronics into standard silicon technology may soon be possible, if experiments confirm a new theoretical prediction by physicists at the Naval Research Laboratory and the University of Wisconsin-Madison.

The researchers predict that a family of well-known silicon surfaces, stabilized by small amounts of gold atoms, is intrinsically magnetic despite having no magnetic elements. None of these surfaces has yet been investigated experimentally for magnetism, but the new predictions are already supported indirectly by existing data. The complete findings of the study are published in the August 24, 2010, issue of the journal Nature Communications.

Silicon provides a unique entry point for combining magnetoelectronics based on single spins with standard electronics technology. If a single-spin device can be built on a silicon wafer, input and output electronics can be directly integrated with the magnetic part of the device. This has been an obstacle for current spintronics approaches. For example, spin injection from a metal into silicon is very inefficient unless the metal/semiconductor interface is carefully optimized.

These latest results have the advantage that nature itself guides, by a self-assembly process, the formation of long chains of polarized electron spins with atomically precise structural order. "This integration of structural and magnetic order is crucial for future technologies based on single spins at the atomic level" said Dr. Steven Erwin, a physicist at NRL and lead theorist on the project.

The magnetic silicon surfaces, one of which is illustrated here, naturally form steps which are stabilized by chains of gold atoms (yellow). According to the team's calculations, some of the silicon atoms at the step edges have unpaired electrons that are fully spin polarized and probably magnetically ordered at sufficiently low temperatures.

The atom chains on the Si(553)-Au surface were discovered in the group of co-author Dr. Franz Himpsel at the University of Wisconsin-Madison. Several other groups worldwide have been investigating such "one-dimensional" silicon surfaces in recent years. As Himpsel noted, "The idea of creating magnetism in a nonmagnetic material by manipulating its structure has long intrigued scientists. The hope of realizing this idea in silicon has been widely discussed for decades, but so far none of these speculations has held up under scrutiny."

The work of Erwin and Himpsel suggests several experiments, such as spin-polarized scanning tunneling microscopy, to test their predictions directly. But there is already indirect experimental evidence to support the possibility of magnetism at silicon surfaces. Two research groups, at Yonsei University in Korea and at Oak Ridge National Laboratory in the US, have found that Si(553)-Au develops periodic "ripples" with two different periodicities at low temperatures. One ripple occurs along the silicon step edges with three times the normal periodicity, and the other along the gold chains with two times the normal periodicity. The prediction of Erwin and Himpsel, shown here, reproduces this pattern perfectly. Moreover, this pattern only emerges when magnetism is allowed in the calculation. When magnetism is "turned off" in the theory, the ripples completely vanish. Thus the observation of threefold and twofold ripples offers indirect - if preliminary - confirmation of magnetism.

Linear chains of spin-polarized atoms provide atomically perfect templates for the ultimate memory and logic, in which a single spin represents a bit. One potential application is a "spin shift register" recently proposed theoretically by Gerald D. Mahan, a theoretical physicist at Pennsylvania State University. Another application is the storage of information in single magnetic atoms. Erwin and Himpsel's work also predicts that the magnitude, and even the sign, of the spin coupling can be changed by doping electrons or holes into surface states. The closely related Si(111)-Au surface can be electron-doped by adsorbates (for example, silicon adatoms) on the surface. By varying this adsorbate population one can perform band-structure engineering with extraordinary precision. The possibility of tuning surface magnetism on Si(553)-Au and its relatives using surface chemistry suggests a fascinating new research direction. This work was supported by the Office of Naval Research and by National Science Foundation awards.

Donna McKinney | EurekAlert!
Further information:
http://www.nrl.navy.mil/media/news-releases/105-10r/

More articles from Physics and Astronomy:

nachricht Magnetic nano-imaging on a table top
20.04.2018 | Georg-August-Universität Göttingen

nachricht New record on squeezing light to one atom: Atomic Lego guides light below one nanometer
20.04.2018 | ICFO-The Institute of Photonic Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Tiny microenvironments in the ocean hold clues to global nitrogen cycle

23.04.2018 | Earth Sciences

Joining metals without welding

23.04.2018 | Trade Fair News

Researchers illuminate the path to a new era of microelectronics

23.04.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>