Properties of vapor-deposited Au:Er films for metallic magnetic calorimeters

Abstract: Prototype metallic magnetic calorimeters (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 ( 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 thick Au:Er films have been investigated from room temperature down to 40mK. The measured magnetization matches theoretical values down to 200mK. 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. [Copyright &y& Elsevier]