Brookhaven Spotlights: News from the March 2001 American Physical Society Meeting

NOTE TO EDITORS: "Brookhaven Spotlights" is issued periodically to bring you up to date on some of the latest newsworthy developments at the U.S. Department of Energy's Brookhaven National Laboratory. The selected briefings below describe research that Brookhaven scientists will present at the American Physical Society meeting to be held March 12-16 at the Washington State Convention Center in Seattle, Washington.

The following information is embargoed for release at the time of each individual talk.  

Research reveals secret of high-performance transducers

Brookhaven's Beatriz Noheda will report on new advances in the study of piezoelectric materials - materials that can be deformed by the application of an electric field, or that produce an electric current when physically deformed. One of the most important piezoelectric materials, known as PZT (a ceramic), is used as a transducer for transforming the vibrations of sound waves, for example, into electrical current and vice versa in devices such as telephones, sonar systems, and ultrasound machines. Noheda will describe the discovery of a previously unknown phase, or crystalline shape, for certain compositions of PZT, which explains their very high piezoelectric response.

"With this new 'monoclinic' phase, you no longer have to apply the electric field in the exact direction of the deformation. This material has a lot more freedom to deform," Noheda says. Scientists may now look for this "monoclinic" phase in other materials and use them as well as PZT to make the next generation of solid-state transducers, which could result in much more sensitive devices. This work was done at the National Synchrotron Light Source.    

Noheda's talk will take place in Room 602-603 on Tuesday, March 13, at 11:35 a.m.  

Scientists explore electronic states in high-temperature superconductors 

Brookhaven's Tonica Valla will present his group's latest efforts to understand the underlying mechanism for superconductivity in copper-based (cuprate) materials that act as high-temperature superconductors. Like traditional superconductors, these materials carry electrical current with no resistance while in their superconducting state. But Valla's studies at the National Synchrotron Light Source reveal that they don't use the same mechanism.      

In both traditional and high-temperature superconductors, pairs of electrons carry the electric current, but the "glue" that holds the pairs together may be different. Valla's experiments give direct information about electronic states in these materials and can uncover the interaction that causes pairing of electrons. "These cuprate materials have properties that cannot be explained by conventional theories," Valla says.     

The motivation for understanding the mechanism is a practical one. The new materials become superconducting at warmer temperatures than conventional superconductors, which must be kept super cold by surrounding them with expensive liquid helium. The cuprates Valla studies are superconducting at temperatures "warm" enough to be chilled by less-expensive liquid nitrogen. "If we understand how these high-temperature superconductors work, we might be able to make them more efficient so that they can take the place of the more expensive kind in magnets for accelerators, electronic circuits, or even more exotic applications as superconducting railroads and motors," Valla says.      

Valla will give this talk in Ballroom 6C on Tuesday, March 13, at 9:12 a.m.  

New x-ray technique improves imaging of breast calcifications

Brookhaven scientist Zhong Zhong and North Carolina State University researchers Miklos Z. Kiss and Dale E. Sayers are investigating a new technique called diffraction enhanced imaging (DEI) to detect and study calcifications of breast tissue. Using DEI, the collaboration looked at a sample of breast tissue with at least ten calcifications and made computer models of the new imaging process to study its contrast mechanisms. This new method significantly improves pictures of breast tissue compared to x-rays used in mammography. Calcifications are associated with breast cancer, and their early detection is crucial for diagnosis and treatment. 

DEI was developed and tested at Brookhaven's National Synchrotron Light Source (NSLS) by researchers from Brookhaven, the Illinois Institute of Technology, North Carolina State University, and the University of North Carolina. DEI reduces the x-ray scattering that makes for blurry images and lack of contrast in mammograms. The new patented method may one day replace mammograms.      

Kiss will describe DEI in Room 606 on Friday, March 16, at 9:12 a.m.  

Scientists probe the properties of mixed magnets

Brookhaven's Andrey Zheludev will review recent neutron scattering studies of "mixed" quantum/classical magnets. Conventional magnets are characterized by long-range magnetic order - where the magnetic fields of all the individual atoms are oriented in the same or alternating directions. In contrast, certain one-dimensional magnets become disordered when quantum effects cause oscillations in the magnetic fields of individual atoms. "The properties of such systems totally defy the classical picture of magnetism," Zheludev says.

An outstanding problem in condensed matter physics is understanding how classical and quantum magnets interact when combined in a single material. Zheludev will describe the discovery and study of the first known experimental example of such "mixed" magnets, found in complex rare-earth nickel oxides. The most important finding is that dynamic properties of these compounds have a unique dual nature, with features of both quantum and classical magnetism.      

This study deals with the most basic and fundamental aspects of material magnetism. While unlikely to result in practical applications in the short term, it contributes to the general understanding of how all magnets work.      

Zheludev's talk will take place in Ballroom 6A on Wednesday, March 14, at 8:00 a.m.For more information on the APS meeting, go to: http://www.aps.org/meet/MAR01/.