Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Giant magnetocaloric materials could have large impact on the environment

20.06.2007
Materials that change temperature in magnetic fields could lead to new refrigeration technologies that reduce the use of greenhouse gases, thanks to new research at the U.S. Department of Energy's Argonne National Laboratory and Ames National Laboratory.

Scientists carrying out X-ray experimentation at the Advanced Photon Source at Argonne — the nation's most powerful source of X-rays for research — are learning new information about magnetocaloric materials that have potential for environmentally friendly magnetic refrigeration systems.

Magnetic refrigeration is a clean technology that uses magnetic fields to manipulate the degree of ordering (or entropy) of electronic or nuclear magnetic dipoles in order to reduce a material's temperature and allow the material to serve as a refrigerant. New materials for refrigeration based on gadolinium-germanium-silicon alloys display a giant magnetocaloric effect due to unusual coupling between the material's magnetism and chemical structure.

Understanding this coupling is essential to moving this technology from the laboratory to the household. Magnetic refrigeration does not rely on hydrofluorocarbons (HFCs) used in conventional refrigeration systems. HFCs are greenhouse gases that contribute to global climate change when they escape into the atmosphere.

A collaboration between researchers from Argonne and Ames has now revealed key atomic-level information about these new materials that makes clear the role played by the nominally non-magnetic germanium-silicon ions in the giant magnetocaloric effect. In an article published in the June 15 issue of Physical Review Letters, the researchers describe how they used high-brilliance, circularly-polarized X-ray beams at the Advanced Photon Source to probe the magnetism of gadolinium and germanium ions as the material underwent its bond-breaking magneto-structural transition. In addition to the expected strong magnetization of gadolinium ions, the researchers found significant magnetization attached to the germanium ions.

“This is surprising and important,” said Argonne physicist Daniel Haskel, who led the research team. “Germanium was expected to be non-magnetic. Its magnetization is induced by the hybridization, or mixing, of otherwise non-magnetic germanium atomic orbitals with the magnetic gadolinium orbitals. This hybridization dramatically changes at the germanium-silicon bond-breaking transition, causing the destruction of magnetic ordering and leading to the giant magnetocaloric effect of these materials.”

By combining the novel experimental results with detailed numerical calculations of the electronic structure carried out at Ames Laboratory, the researchers were able to conclude that the magnetized germanium orbitals act as “magnetic bridges” in mediating the magnetic interactions across the distant gadolinium ions.

The magnetocaloric effect – a change in temperature accompanying a change in a material's magnetization – is largest near a material's intrinsic magnetic ordering temperature. In the case of rare-earth gadolinium, this ordering occurs near room temperature and results in a temperature increase of 3-4 K/per Tesla when a magnetic field is applied, making gadolinium the current material of choice for magnetic refrigeration near room temperature.

The prospects for a viable magnetic refrigeration technology recently became brighter with the report of a giant magnetocaloric effect in gadolinium-silicon-germanium alloys. The addition of non-magnetic silicon and germanium ions brings about a giant entropy change when germanium-silicon chemical bonds connecting the magnetism-carrying gadolinium ions are quickly formed or broken, respectively, by the application or removal of a magnetic field. As an added bonus, the magnetic ordering temperature can be tuned by changing the ratio or germanium to silicon.

"As a result of this work we now have a better understanding of the role of nonmagnetic elements, such as germanium, in enhancing magnetic interactions between the rare-earth metals in these materials,” said co-author and Ames Laboratory senior scientist Vitalij Pecharsky. “This discovery is counterintuitive, yet it opens up a range of exciting new opportunities towards the engineering of novel magnetic materials with predictable properties."

Other authors in the paper are Y. Lee, B. Harmon, Y. Mudryk, and K. Gschneidner of Ames and Z. Islam, J. Lang, and G. Srajer at Argonne.

Ames Laboratory, celebrating its 60th anniversary in 2007, is operated for the Department of Energy by Iowa State University. The Lab conducts research into various areas of national concern, including energy resources, the synthesis and study of new materials, high-speed computer design, and environmental cleanup and restoration.

With employees from more than 60 nations, Argonne National Laboratory brings the world's brightest scientists and engineers together to find exciting and creative new solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America 's scientific leadership and prepare the nation for a better future. Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.

For more information, please contact Sylvia Carson (630/252-5510 or scarson@anl.gov) at Argonne.

Sylvia Carson | EurekAlert!
Further information:
http://www.anl.gov

More articles from Physics and Astronomy:

nachricht The moon is front and center during a total solar eclipse
24.07.2017 | NASA/Goddard Space Flight Center

nachricht Superluminous supernova marks the death of a star at cosmic high noon
24.07.2017 | Royal Astronomical Society

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: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

Ultrathin device harvests electricity from human motion

24.07.2017 | Power and Electrical Engineering

Scientists announce the quest for high-index materials

24.07.2017 | Materials Sciences

ADIR Project: Lasers Recover Valuable Materials

24.07.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>