Development of ferromagnetic shape memory alloy - silicon bimorph nanoactuators

This paper presents the development and fabrication of first-of-its kind free-standing ferromagnetic shape memory alloy (FSMA)/Si bimorph cantilevers. The exploitation of FSMAs such as Ni-Mn-Ga is of large interest for nanoactuation due to their multifunctional ferromagnetic and shape memory properties allowing for large work density. A new nanofabrication process is developed consisting of electron-beam lithography, Si reactive ion etching and the deposition of Ni-Mn-Ga films on pre-structured Si substrates. For decreasing dimensions of Si nanocantilevers, a pronounced size effect of self-organized FSMA deposition is observed once the cantilever width matches the grain size of 100 nm, which is comparable to the size of magnetic domains.