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H. Eguchi (Brown University), R. Bruni (Harvard-Smithsonian Center for Astrophysics), Y. H. Huang, A. N. Mocharnuk-Macchia (Brown University), S. Romaine (Harvard-Smithsonian Center for Astrophysics), G. M. Seidel, B. Sethumadhavan, W. Yao (Brown University)
The next generation x-ray astronomy satellite missions such as Constellation-X will utilize a cryogenic microcalorimeter for high energy resolution (\Delta E=2 eV up to 10 keV) x-ray spectroscopy. The more recent technology, metallic magnetic calorimeters (MMCs) has shown comparable energy resolution to TES and other microcalorimeters. A prototype MMC, in which the magnetization of Au:Er sensors has been measured using a DC SQUID, have shown excellent energy resolution for soft x-rays. However, the results to date have been obtained with devices assembled by hand, placing a small (~50 \mum diameter), thin disk of the Au:Er alloy within the loop of the SQUID. This is an unacceptable method for fabricating large focal-plane arrays of detectors required for the next generation of x-ray telescopes. We are therefore investigating the properties of vapor-deposited films produced by DC magnetron sputtering using an Au:Er alloy target. The magnetic properties of five micron thick Au:Er films have been investigated from room temperature down to 40 mK. The measured magnetization matches theoretical values down to 200 mK. The films have the same Er concentration as in the target material. At lower temperatures there is indication of enhanced magnetic interactions among the Er ions. We are studying the dependence of this interaction on the parameters used in the deposition process. This work is supported by NASA grants NAG5-10383 and APRA04-0000-0157
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.