Martensitic transition and magnetoresistance in a Cu-Al-Mn shape memory alloy. Influence of aging

Abstract

We have studied the effect of ageing within the miscibility gap on the electric, magnetic and thermodynamic properties of a non-stoichiometric Heusler Cu-Al-Mn shape-memory alloy, which undergoes a martensitic transition from a $bcc$-based ($\beta$-phase) towards a close-packed structure ($M$-phase). Negative magnetoresistance which shows an almost linear dependence on the square of magnetization with different slopes in the $M$- and $\beta$-phases, was observed. This magnetoresistive effect has been associated with the existence of Mn-rich clusters with the Cu${}_2$AlMn-structure. The effect of an applied magnetic field on the martensitic transition has also been studied. The entropy change between the $\beta$- and $M$-phases shows negligible dependence on the magnetic field but it decreases significantly with annealing time within the miscibility gap. Such a decrease is due to the increasing amount of Cu${}_2$MnAl-rich domains that do not transform martensitically.

9 pages, 9 figures, accepted for publication in PRB

References in corpus (1)

• Magnetic phase separation in ordered alloys

Cited by in corpus (5)

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• Low temperature irreversibility induced by thermal cycles on two prototypical phase separated manganites
• Thermal cycling effects on static and dynamic properties of a phase separated manganite