SLAC Today is available online at:
http://today.slac.stanford.edu
In this issue:
Protecting Future Hard Drives
Science Today: A Step Toward Understanding High-Temperature Superconductors
SLAC Hires ES&H Division Director
Come Thank Communications Director Neil Calder

SLAC Today

Thursday - December 13, 2007

Protecting Future Hard Drives

SSRL scientist Mike Toney (left) and Ricardo Ruiz from Hitachi.

The newest iPod can store every episode of The Simpsons that ever aired and still fit into an Altoids can—and the next version will hold more data in an even tinier package. Consumers have a voracious appetite for data storage capacity, and with the help of Stanford's Synchrotron Radiation Laboratory (SSRL), Hitachi Global Storage Technologies is striving to keep up with the demands.

Ricardo Ruiz, a Research Staff Member at Hitachi in San Jose, is using Beamline 2-1 to help develop the next generation of hard disk drives. "My particular project involves the material that protects the magnetic recording surface of hard drives—from scratches, corrosion and other forms of damage," he explained. Currently, high-quality overcoats are made from hydrogenated carbon and are about 15 nanometers thick. But as the data capacity of hard disk drives continues to increase, the density of the magnetic domains storing the information must scale up accordingly. Consequently, the distance between the disk reader and the disk surface must move closer together, demanding a thinner overcoat.

"That's a problem because the overcoat has to be very thin but still protect the magnetic medium," said Ruiz. "Carbon is reaching its limits, so we need to find a replacement." One promising alternative to carbon is silicon nitride. "It's very dense—much denser than carbon," Ruiz said. "It has real potential."  Read more...

(Daily Column - Science Today)

A Step Toward Understanding High-Temperature Superconductors

Scientists can make high-temperature superconductors, but they don't have a good theory for how they work. Understanding high-temperature superconductors will have significant impact on the modern condensed matter theory, and may someday allow scientists to design room-temperature superconductors. SLAC Photon Science and Stanford Professor Z.-X. Shen and colleagues, working at SSRL's Beam Line 5-4, recently made observations that will help shape the theory. Their results are published in the Nov. 1 issue of Nature.

Certain materials become superconductors—that is, losing all resistance to electric current—when they become colder than their transition temperature. So far, the warmest transition temperature recorded is minus 164 degrees Fahrenheit. Below the transition temperature, the electrons pair up. This pairing reduces the energy of the electrons. The strength of pairing is characterized as a superconducting gap in the single particle excitation spectrum, which is found below the transition temperature in both conventional and high-temperature superconductors.

In high-temperature superconductors, scientists also observe a gap above the transition temperature, called the pseudogap. So far it has been unclear whether the two gaps are unrelated, or if the pseudogap is a precursor to the superconducting gap. Using angle-resolved photoemission spectroscopy to measure the energy gap at different temperatures and momenta, Shen and colleagues found that the pseudogap and the superconducting gap coexist and exhibit different temperature dependence. Therefore, the two gaps seem to have different origins. This should provide an important step toward unveiling the mystery of the pseudogap phenomena. More information about this research can be found in the full scientific highlight.

SLAC Hires ES&H Division Director

(Photo - Craig Ferguson)SLAC is extremely pleased to announce that Craig Ferguson, currently the Environment, Safety, Health and Quality (ESH&Q) Associate Director at Jefferson Laboratory, has accepted the position of Division Director of Environment, Safety and Health (ES&H) at SLAC.

Ferguson has nearly 20 years experience in safety management and safety related positions, including time at the Oak Ridge Y-12 facility, BWX Technologies, and EG & G, in addition to Jefferson Lab. He has a track record of success in improving the ES&H performance at each facility where he has worked. SLAC Today will publish more information about Ferguson when he arrives at the lab early next year.


Come Thank Communications Director Neil Calder

Come bid adieu to Communications Director Neil Calder this afternoon at 2:30 p.m. in the Research Office Building's Redwood Rooms!

As always, the communications office will revel in style as we celebrate our fearless leader. All are invited to attend. We look forward to seeing you there!


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