Oak Ridge Today

Four ORNL researchers elected fellows of American Physical Society

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Jaime Fernandez-Baca

Jaime Fernandez-Baca (Photo courtesy ORNL)

Four researchers from Oak Ridge National Laboratory have been elected fellows of the American Physical Society, one of the nation’s top professional organizations for scientists.

Jaime Fernandez-Baca, Sergei Kalinin, Mark Lumsden, and Thomas Maier were selected for the honor by the APS Council of Representatives. They will be formally recognized at the APS’s March meeting.

Fernandez-Baca, a distinguished research staff member in the Quantum Condensed Matter Division in ORNL’s Neutron Science Directorate, was recognized by the APS Division of Materials Physics “for seminal neutron scattering studies of magnetic materials, especially the spin and lattice dynamics of colossal magnetoresistive manganites.”

Fernandez-Baca’s research is performed mainly at ORNL’s High Flux Isotope Reactor, where he is the lead for the Triple Axis Spectroscopy group. His expertise is in the study of the magnetic ordering and spin dynamics of complex oxides and related alloys using neutron scattering techniques.

He was the recipient of the International Atomic Energy Agency fellowship, the DOE Office of Science Outstanding Mentor Award (2008), and the Neutron Scattering Society of America Distinguished Service Award (2014). [Read more…]

ORNL scientists uncover clues to role of magnetism in iron-based superconductors

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Magnetism of Iron-based Superconductors

Oak Ridge National Laboratory scientists used scanning transmission electron microscopy to measure atomic-scale magnetic behavior in several families of iron-based superconductors. (Photo courtesy ORNL)

 

New measurements of atomic-scale magnetic behavior in iron-based superconductors by researchers at Oak Ridge National Laboratory and Vanderbilt University are challenging conventional wisdom about superconductivity and magnetism.

The study published in Advanced Materials provides experimental evidence that local magnetic fluctuations can influence the performance of iron-based superconductors, which transmit electric current without resistance at relatively high temperatures.

“In the past, everyone thought that magnetism and superconductivity could not coexist,” said ORNL’s Claudia Cantoni, the study’s first author. “The whole idea of superconductors is that they expel magnetic fields. But in reality things are more complicated.”

Superconductivity is strongly suppressed by the presence of long-range magnetism—where atoms align their magnetic moments over large volumes—but the ORNL study suggests that rapid fluctuations of local magnetic moments have a different effect. Not only does localized magnetism exist, but it is also correlated with a high critical temperature, the point at which the material becomes superconducting. [Read more…]

ORNL study advances quest for better superconducting materials

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Superconductivity Pan Defects

Minghu Pan’s image of “clover-like” atomic defects—an example is circled—that result in strong superconductivity. (Photo courtesy ORNL)

Nearly 30 years after the discovery of high-temperature superconductivity, many questions remain, but an Oak Ridge National Laboratory team is providing insight that could lead to better superconductors.

Their work, published in Physical Review Letters, examines the role of chemical dopants, which are essential to creating high-temperature superconductors—materials that conduct electricity without resistance. The role of dopants in superconductors is particularly mysterious as they introduce non-uniformity and disorder into the crystal structure, which increases resistivity in non-superconducting materials.

By gaining a better understanding of how and why chemical dopants alter the behavior of the original (parent) material, scientists believe they can design superconductors that work at higher temperatures. This would make them more practical for real-world wire applications because it would lessen the extreme cooling required for conventional superconducting material. Existing “high-temperature superconductors” operate at temperatures in the range of negative 135 degrees Celsius and below. [Read more…]