Mo. Prado et Fc. Lovey, MAGNETIC-PROPERTIES AND MARTENSITIC-TRANSFORMATION IN CU-MN-AL ALLOYS, Anales de la Asociacion Quimica Argentina, 84(4), 1996, pp. 367-370
CuMnAl alloys with compositions Cu3Al1-xMn2x, where 0<x<0.26, undergo
chemical ordering reactions of the type A2-->B2-->DO3-L2(1) during que
nching from 1123K into water at room temperature [1], retaining the me
tastable beta phase. At lower temperatures they transform to close pac
ked 18R or 2H martensites [2]. From about 90K to room temperature Mn a
toms respond to an applied magnetic field as clusters of ferromagneti
cally coupled atoms, behaving as superparamagnets. The A(s) (martensit
e-->beta) temperature is independent on the applied magnetic field up
to 5 Tesla. Both, beta and martensite phases, exhibit at lower tempera
tures mictomagnetism, it is to say a mixture of ferromagnetism and ant
iferromagnetism. This can be understood in terms of the Mn-Mn distance
s. Antiferromagnetism in beta and martensite phases, is mainly due to
inherited chemical disorder during quenching.