TEM STUDIES IN MELT-SPUN CU-MN-AL SYSTEM EXHIBITING GIANT MAGNETORESISTANCE

Giant magnetoresistance (GMR) has recently been observed in a new syst em, melt-spun ribbons of Cu-Mn-Al, with Delta R/R(0) = 15% at 30 K. Th e GMR behavior in this system has been extensively studied for a range of compositions. It is suggested that the onset of GMR may be attribu ted to the appearance of tweed microstructure in the ferromagnetic Cu2 MnAl phase. It has also been observed that GMR existed in all samples consisting of a mixture of varying amounts of Cu2MnAl and CU9Al4 phase s. Extensive transmission electron microscopy studies have been carrie d out to evaluate the microstructural evolution of the tweed and the o bserved phases, and to correlate the microstructure with the observed GMR behavior.