TEM studies in melt-spun Cu-Mn-Al system exhibiting giant magnetoresistance

Giant magnetoresistance (GMR) has recently been observed in a new system, melt-spun ribbons of Cu-Mn-Al, with /spl Delta/R/R(0)=15% at 30 K. The GMR behavior in this system has been extensively studied for a range of compositions. It is suggested that the onset of GMR may be attributed to the appearance of tweed microstructure in the ferromagnetic Cu/sub 2/MnAl phase. It has also been observed that GMR existed in all samples consisting of a mixture of varying amounts of Cu/sub 2/MnAl and Cu/sub 9/Al/sub 4/ phases. Extensive transmission electron microscopy studies have been carried out to evaluate the microstructural evolution of the tweed and the observed phases, and to correlate the microstructure with the observed GMR behavior.