STRUCTURAL EVOLUTION OF A CU1-XCOX ALLOY DURING THERMAL HEATING STUDIED BY ACOUSTIC SPECTROSCOPY

A granular CuCo alloy prepared by melt-spinning has a giant magnetores istance (GMR) effect, whose magnitude depends on thermal treatment, Co concentration, and synthesis conditions. In this paper, the microstru cture evolution of Cu1-xCox alloy during heating has been investigated by acoustic spectroscopy (internal friction) measurements. It is show n that the nucleation of Co particles occurs at the copper grain bound aries as a consequence of the thermal annealing. Moreover, the high te mperature internal friction is directly connected with the presence of Co precipitates in the Cu matrix, depending on the quenching rate and the Co concentration. The results clearly indicate that a careful con trol of the synthesis parameters is necessary to obtain optimum magnet oresistive behavior. (C) 1998 Elsevier Science B.V. All rights reserve d.