Magnetoelasticity and magnetoresistance in Cu-Al-Mn shape-memory alloys

This paper is aimed at studying the effect of a magnetic field on the marte nsitic transition of a Cu-Al-Mn shape-memory alloy. The martensitic transit ion has been studied through resistance measurements under applied magnetic fields ranging from 0 to 50 kOe. Negative,magnetoresistance showing an alm ost linear dependence with the square of the magnetization has been observe d. This magnetoresistive effect is associated with the existence of small f erromagnetic Mn-clusters. Its strength and thermal dependence is different in both phases. The martensitic transition temperature is slightly increase d and its spread in temperature significantly reduced upon increasing the f ield. These results show the existence of magnetoelastic coupling, which fa vors the nucleation of those martensitic variants with the easy magnetizati on axis aligned with the field.