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Spontaneous strains during martensitic transformation and magnetic-field-induced transformation have been systemically studied for Ni46Cu4Mn38Sn12 Heusler alloy, respectively. A large spontaneous strain with the value of about 0.12% upon martensitic transformation has been observed in this alloy, which is almost three times larger than that in ternary Ni–Mn–Sn alloy. In addition, such a value of strain can be obtained through a fully reverse martensitic transformation induced by a field of about 45 kOe, exhibiting a considerable metamagnetic shape memory effect without any prestrain. This behavior can be attributed to magnetoelastic coupling between stable martensite and metastable fraction of austenite.

The electronic and magnetic structures of both bcc and fcc ordered Ni x Mn 1-x alloys, with x = 0, 0.25, 0.5, 0.75, and 1, are performed using the first principle linearized augmented plane-wave (LAPW) method within the framework of local spin-density functional approximation (LSDA). It is shown that fcc Ni x Mn 1-x with x = 1, 0.75 is ferromagnetic ordering, which is in good agreement with the experiments. At the equiatomic composition of Ni x Mn 1-x with x = 0.5, it is antiferromagnetic ordering. With the lower Ni composition, it presents ferrimagnetic and antiferromagnetic ordering, respectively. For bcc Ni x Mn 1-x with both rich Ni and rich Mn composition, however, it presents ferromagnetic and ferrimagnetic ordering, respectively. At the equiatomic Ni x Mn 1-x with x = 0.5, it presents ferromagnetic ordering.

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