Combinatorial Investigation of Ferromagnetic Shape-Memory Alloys in the Ni-Mn-Al Ternary System Using a Composition Spread Technique

Using a thin-film composition spread technique, we have mapped the phase diagram of the Ni-Mn-Al ternary system in search of ferromagnetic shape-memory alloys (FMSA). A characterization technique that allows detection of martensitic transitions by visual inspection using micromachined cantilever arrays was combined with quantitative magnetization mapping using scanning superconducting quantum interference device (SQUID) microscopy. A large compositional region in the Al deficient part of the phase diagram was found to be ferromagnetic and reversibly martensitic at room temperature. In addition, in the Al rich region, a new compositional range that displays marked ferromagnetism was found.