Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


android tablet pc

Home > Press > Nano magnets arise at 2-D boundaries: Rice University theory has implications for spintronics

Rice University theorists have discovered magnetic fields (blue) are created at grain boundaries in two-dimensional dichalcogenides. Dislocations along these boundaries, where atoms are thrown out of their regular hexagonal patterns, force electron spins into alignments that favor magnetism.Credit: Zhuhua Zhang/Rice University
Rice University theorists have discovered magnetic fields (blue) are created at grain boundaries in two-dimensional dichalcogenides. Dislocations along these boundaries, where atoms are thrown out of their regular hexagonal patterns, force electron spins into alignments that favor magnetism.

Credit: Zhuhua Zhang/Rice University

Abstract:
When you squeeze atoms, you don't get atom juice. You get magnets.

According to a new theory by Rice University scientists, imperfections in certain two-dimensional materials create the conditions by which nanoscale magnetic fields arise.

Nano magnets arise at 2-D boundaries: Rice University theory has implications for spintronics

Houston, TX | Posted on November 14th, 2013

Calculations by the lab of Rice theoretical physicist Boris Yakobson show these imperfections, called grain boundaries, in two-dimensional semiconducting materials known as dichalcogenides can be magnetic. This may lead to new strategies for the growing field of spintronics, which takes advantage of the intrinsic spin of electrons and their associated magnetic fields for electronic and computing devices.

The discovery by Yakobson, lead author Zhuhua Zhang and their colleagues was reported online this week in the American Chemical Society journal ACS Nano.

Dichalcogenides are hybrids that combine transition metal and chalcogen atoms, which include sulfur, selenium and tellurium. The Yakobson group focused on semiconducting molybdenum disulfide (MDS) that, like atom-thick graphene, can be grown via chemical vapor deposition (CVD), among other methods. In a CVD furnace, atoms arrange themselves around a catalyst seed into familiar hexagonal patterns; however, in the case of MDS, sulfur atoms in the lattice alternately float above and below the layer of molybdenum.

When two growing blooms meet, they're highly unlikely to line up, so the atoms find a way to connect along the border, or grain boundary. Instead of regular hexagons, the atoms are forced to find equilibrium by forming adjoining rings known as dislocations, with either five-plus-seven nodes or four-plus-eight nodes.

In graphene, which is generally considered the strongest material on Earth, these dislocations are weak points. But in MDS or other dichalcogenides, they have unique properties.

"It doesn't matter how you grow them," Yakobson said. "These misoriented areas eventually collide, and that's where you find topological defects. It turns out that - and I like this mechanistic metaphor - they squeeze magnetism out of nonmagnetic material."

In previous work, Yakobson found dislocations create atom-width conducting lines and dreidel-shaped polyhedra in MDS. This time, the team dug deeper to find that dislocation cores turn magnetic where they force spinning electrons to align in ways that don't cancel each other out, as they do in a flawless lattice. The strength of the magnets depends on the angle of the boundary and rises with the number of dislocations necessary to keep the material energetically stable.

"Every electron has charge and spin, both of which can carry information," Zhang said. "But in conventional transistors, we only exploit the charge, as in field-effect transistors. For newly emerged spintronic devices, we need to control both charge and spin for enhanced efficiency and enriched functions."

"Our work suggests a new degree of freedom -- a new controlling knob -- for electronics that use MDS," Yakobson said. "The ability to control the magnetic properties of this 2-D material makes it superior to graphene in certain respects."

He said the dislocation rings of four and eight atoms are not energetically favored in graphene and unlikely to occur there. But in the materials that mix two elements, certain grain boundary configurations will very likely create conditions where similar elements, wishing to avoid contact with each other, will instead bond with their chemical opposites.

"The system avoids mono-elemental bonds," Yakobson said. "The chemistry doesn't like it, so four-eight offers a benefit." Those defects are also the strongest sources of magnetism at certain grain boundary angles, he said; at some angles, the boundaries become ferromagnetic.

The team proved its theory through computer models designed to isolate and control the effects of the nanoribbons' edges and grain boundary dipoles that could skew the results. They also determined that grain boundary angles between 13 and 32 degrees force a progressive overlap between the dislocations' spins. With sufficient overlap, the spins become magnetically coupled and broaden into electronic bands that support spin-polarized charge transport along the boundary.

Now, Yakobson said, "The challenge is to find a way to experimentally detect these things. It's quite difficult to resolve it at this spatial resolution, especially when some of the experimental methods, like electron beams, would destroy the material."

Co-authors of the paper are Rice postdoctoral researcher Xiaolong Zou and Vincent Crespi, distinguished professor of physics, materials science and engineering, and chemistry at The Pennsylvania State University. Yakobson is Rice's Karl F. Hasselmann Professor of Mechanical Engineering and Materials Science, a professor of chemistry and a member of the Richard E. Smalley Institute for Nanoscale Science and Technology.

A U.S. Army Research Office Multidiscipline University Research Initiative grant, the National Science Foundation and the Robert Welch Foundation supported the research. Computations were performed on the Data Analysis and Visualization Cyberinfrastructure supercomputer administered by Rice's Ken Kennedy Institute for Information Technology.

####

About Rice University
Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,708 undergraduates and 2,374 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice has been ranked No. 1 for best quality of life multiple times by the Princeton Review and No. 2 for "best value" among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to tinyurl.com/AboutRiceU.

Follow Rice News and Media Relations via Twitter @RiceUNews

For more information, please click here

Contacts:
David Ruth
713-348-6327


Mike Williams
713-348-6728

Copyright © Rice University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

Read the abstract at:

Yakobson Research Group:

Related News Press

News and information

The International Space Elevator Consortium (ISEC) is proud to announce the 2014 Space Elevator Conference! This annual event will be held at the Museum of Flight in Seattle, Washington from Friday, August 22nd through Sunday, August 24th August 19th, 2014

KaSAM-2014 International Conference (September 7-10, 2014, Kathmandu, Nepal) August 19th, 2014

Success in Intracellular Imaging of Cesium Distribution in Plants Used for Cesium Absorption August 19th, 2014

Electrical engineers take major step toward photonic circuits: Team invents non-metallic metamaterial that enables them to 'compress' and contain light August 19th, 2014

Govt.-Legislation/Regulation/Funding/Policy

Success in Intracellular Imaging of Cesium Distribution in Plants Used for Cesium Absorption August 19th, 2014

Electrical engineers take major step toward photonic circuits: Team invents non-metallic metamaterial that enables them to 'compress' and contain light August 19th, 2014

Promising Ferroelectric Materials Suffer From Unexpected Electric Polarizations: Brookhaven Lab scientists find surprising locked charge polarizations that impede performance in next-gen materials that could otherwise revolutionize data-driven devices August 18th, 2014

Novel chip-based platform could simplify measurements of single molecules: A nanopore-gated optofluidic chip combines electrical and optical measurements of single molecules onto a single platform August 14th, 2014

Spintronics

Molecular engineers record an electron's quantum behavior August 14th, 2014

Diamond defect interior design: Planting imperfections called 'NV centers' at specific spots within a diamond lattice could advance quantum computing and atomic-scale measurement August 5th, 2014

University of Illinois study advances limits for ultrafast nano-devices July 10th, 2014

Harnessing magnetic vortices for making nanoscale antennas: Scientists explore ways to synchronize spins for more powerful nanoscale electronic devices April 30th, 2014

Quantum Computing

Molecular engineers record an electron's quantum behavior August 14th, 2014

Diamonds are a Quantum Computer’s Best Friend: A new kind of quantum computer is being proposed by scientists from the TU Wien (Vienna) and Japan (National Institute of Informatics and NTT Basic Research Labs) August 8th, 2014

Diamond defect interior design: Planting imperfections called 'NV centers' at specific spots within a diamond lattice could advance quantum computing and atomic-scale measurement August 5th, 2014

Watching Schrödinger's cat die (or come to life): Steering quantum evolution & using probes to conduct continuous error correction in quantum computers July 30th, 2014

Discoveries

Success in Intracellular Imaging of Cesium Distribution in Plants Used for Cesium Absorption August 19th, 2014

Сalculations with Nanoscale Smart Particles August 19th, 2014

Electrical engineers take major step toward photonic circuits: Team invents non-metallic metamaterial that enables them to 'compress' and contain light August 19th, 2014

Graphene rubber bands could stretch limits of current healthcare, new research finds August 19th, 2014

Announcements

Сalculations with Nanoscale Smart Particles August 19th, 2014

Life on Mars? Implications of a newly discovered mineral-rich structure August 19th, 2014

Harris & Harris Group Letter to Shareholders on Website August 19th, 2014

Electrical engineers take major step toward photonic circuits: Team invents non-metallic metamaterial that enables them to 'compress' and contain light August 19th, 2014

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals

Success in Intracellular Imaging of Cesium Distribution in Plants Used for Cesium Absorption August 19th, 2014

Сalculations with Nanoscale Smart Particles August 19th, 2014

Life on Mars? Implications of a newly discovered mineral-rich structure August 19th, 2014

Promising Ferroelectric Materials Suffer From Unexpected Electric Polarizations: Brookhaven Lab scientists find surprising locked charge polarizations that impede performance in next-gen materials that could otherwise revolutionize data-driven devices August 18th, 2014

Military

New material could enhance fast and accurate DNA sequencing August 13th, 2014

On the frontiers of cyborg science August 10th, 2014

Advanced thin-film technique could deliver long-lasting medication: Nanoscale, biodegradable drug-delivery method could provide a year or more of steady doses August 6th, 2014

Air Force’s 30-year plan seeks 'strategic agility' August 1st, 2014

Research partnerships

Сalculations with Nanoscale Smart Particles August 19th, 2014

Promising Ferroelectric Materials Suffer From Unexpected Electric Polarizations: Brookhaven Lab scientists find surprising locked charge polarizations that impede performance in next-gen materials that could otherwise revolutionize data-driven devices August 18th, 2014

Nano Bonds Increase Raw Strength of Fireproof Concretes August 18th, 2014

Production of Toxic Ion Nanosorbents with High Sorption Capacity in Iran August 17th, 2014

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More














ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2014 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE