Magnetism piece fits no-resistance puzzle. (Physics).Physicists hotly debate why certain copper oxide Noun 1. copper oxide - an oxide of copper oxide - any compound of oxygen with another element or a radical crystals can conduct electricity without resistance, or superconduct, at temperatures far higher than conventional superconductors can. Now, a German-French-Russian team led by Bernhard Keimer of the Max Planck Institute for Solid State Research The Max Planck Institute for Solid State Research (MPI-FKF) is part of the Max Planck Society which operates 80 research facilities in Germany. It is a research institute located in Büsnau which is part of Stuttgart, Germany. in Stuttgart, Germany, reports crucial evidence that a magnetic feature of the copper oxide plays a role. Many atoms have a magnetic property called spin, which makes them behave as tiny bar magnets. Scientists noticed in experiments even 10 years ago that at a temperature just below the superconductivity superconductivity, abnormally high electrical conductivity of certain substances. The phenomenon was discovered in 1911 by Kamerlingh Onnes, who found that the resistance of mercury dropped suddenly to zero at a temperature of about 4.2°K;. threshold, the spins of many atoms in some copper oxide compounds fluctuated in a coordinated manner. Many scientists dismissed those magnetic behaviors as irrelevant to the so-called high-temperature superconductors' loss of resistance. That's because the traits hadn't shown up in the first of those compounds, a lanthanum-containing material discovered in 1986 (SN: 11/18/00, p. 330). That material harbored only single layers of copper oxide, whereas the newer materials that show the spin phenomenon have double layers. The lanthanum lanthanum (lăn`thənəm) [Gr.,=to lie hidden], metallic chemical element; symbol La; at. no. 57; at. wt. 138.9055; m.p. about 920°C;; b.p. about 3,460°C;; sp. gr. 6.19 at 25°C;; valence +3. material was the only single-oxide-layer superconductor A material that has little resistance to the flow of electricity. Traditional superconductors operate at absolute zero (-459.67 degrees Fahrenheit or -273.15 degrees Celsius). Experiments in the 1980s raised the temperature to -321 degrees Fahrenheit. that could be grown large enough to test for the spin phenomenon. To get around that obstacle, Keimer and his colleagues spent months painstakingly hand-aligning small crystals of thallium thallium (thăl`ēəm), metallic chemical element; symbol Tl; at. no. 81; at. wt. 204.383; m.p. 303.5°C;; b.p. about 1,457°C;; sp. gr. 11.85 at 20°C;; valence +1 or +3. barium copper oxide-a single-oxide-layer compound--and gluing them onto aluminum plates. The result was a system that models a single-oxide-layer crystal big enough for magnetic analysis using a neutron beam. The team describes its work in the Feb. 8 Science. Just below the thallium compound's threshold superconducting temperature of 90 kelvins, the scientists detected the telltale sign of the fluctuating magnetic pattern. Now "it's pretty much been proven that the [spin coordination] is present for all high-temperature superconductors," comments Andrey V. Chubukov of the University of Wisconsin-Madison “University of Wisconsin” redirects here. For other uses, see University of Wisconsin (disambiguation). A public, land-grant institution, UW-Madison offers a wide spectrum of liberal arts studies, professional programs, and student activities. . --P.W |
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