Nanotechnology Now





Heifer International

Wikipedia Affiliate Button


DHgate

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

Leti Announces Launch of First European Nanomedicine Characterisation Laboratory: Project Combines Expertise of 9 Partners in 8 Countries to Foster Nanomedicine Innovation and Facilitate Regulatory Approval July 1st, 2015

Bruker Introduces Second-Generation Inspire Nanochemical Imaging Solution: Featuring Unique PeakForce IR and IR EasyAlign Technology July 1st, 2015

GLOBALFOUNDRIES Completes Acquisition of IBM Microelectronics Business: Transaction adds differentiating technologies, world-class technologists, and intellectual property July 1st, 2015

Samsung's New Graphene Technology Will Double Life Of Your Lithium-Ion Battery July 1st, 2015

Govt.-Legislation/Regulation/Funding/Policy

Carnegie Mellon chemists characterize 3-D macroporous hydrogels: Methods will allow researchers to develop new 'smart' materials June 30th, 2015

Graphene flexes its electronic muscles: Rice-led researchers calculate electrical properties of carbon cones, other shapes June 30th, 2015

X-rays and electrons join forces to map catalytic reactions in real-time: New technique combines electron microscopy and synchrotron X-rays to track chemical reactions under real operating conditions June 29th, 2015

Graphene breakthrough as Bosch creates magnetic sensor 100 times more sensitive than silicon equivalent June 28th, 2015

Spintronics

Spintronics advance brings wafer-scale quantum devices closer to reality June 24th, 2015

Solvent encapsulation is the trick: a solid material with spin-transition solution-like behaviour June 5th, 2015

Oxford Instruments welcomes Dr Masamitsu Hayashi, the winner of the Sir Martin Wood Science Prize for Japan, to UK June 1st, 2015

New options for spintronic devices: Switching magnetism between 1 and 0 with low voltage near room temperature May 18th, 2015

Quantum Computing

Opening a new route to photonics Berkeley lab researchers find way to control light in densely packed nanowaveguides June 27th, 2015

Spintronics advance brings wafer-scale quantum devices closer to reality June 24th, 2015

Harris & Harris Group Portfolio Company D-Wave Systems Announces 1,000 Qubit Processor and is Discussed in the Economist June 23rd, 2015

Discovery paves way for new kinds of superconducting electronics June 22nd, 2015

Discoveries

Measurement of Tiny Amounts of Heavy Metals in Baby Food Samples July 1st, 2015

Chitosan coated, chemotherapy packed nanoparticles may target cancer stem cells June 30th, 2015

Graphene flexes its electronic muscles: Rice-led researchers calculate electrical properties of carbon cones, other shapes June 30th, 2015

Researchers from the UCA, key players in a pioneering study that may explain the origin of several digestive diseases June 30th, 2015

Announcements

Leti Announces Launch of First European Nanomedicine Characterisation Laboratory: Project Combines Expertise of 9 Partners in 8 Countries to Foster Nanomedicine Innovation and Facilitate Regulatory Approval July 1st, 2015

Bruker Introduces Second-Generation Inspire Nanochemical Imaging Solution: Featuring Unique PeakForce IR and IR EasyAlign Technology July 1st, 2015

GLOBALFOUNDRIES Completes Acquisition of IBM Microelectronics Business: Transaction adds differentiating technologies, world-class technologists, and intellectual property July 1st, 2015

Samsung's New Graphene Technology Will Double Life Of Your Lithium-Ion Battery July 1st, 2015

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

Samsung's New Graphene Technology Will Double Life Of Your Lithium-Ion Battery July 1st, 2015

Measurement of Tiny Amounts of Heavy Metals in Baby Food Samples July 1st, 2015

Graphene flexes its electronic muscles: Rice-led researchers calculate electrical properties of carbon cones, other shapes June 30th, 2015

Researchers from the UCA, key players in a pioneering study that may explain the origin of several digestive diseases June 30th, 2015

Military

Graphene flexes its electronic muscles: Rice-led researchers calculate electrical properties of carbon cones, other shapes June 30th, 2015

The peaks and valleys of silicon: Team of USC Viterbi School of Engineering Researchers introduce new layered semiconducting materials as silicon alternative June 27th, 2015

Opening a new route to photonics Berkeley lab researchers find way to control light in densely packed nanowaveguides June 27th, 2015

World’s 1st Full-Color, Flexible, Skin-Like Display Developed at UCF June 24th, 2015

Research partnerships

Leti Announces Launch of First European Nanomedicine Characterisation Laboratory: Project Combines Expertise of 9 Partners in 8 Countries to Foster Nanomedicine Innovation and Facilitate Regulatory Approval July 1st, 2015

Carnegie Mellon chemists characterize 3-D macroporous hydrogels: Methods will allow researchers to develop new 'smart' materials June 30th, 2015

Graphene flexes its electronic muscles: Rice-led researchers calculate electrical properties of carbon cones, other shapes June 30th, 2015

June 29th, 2015

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