Abstract. The giant magneto-strain effect is particularly attractive for actuator applications in micro-and nanometer dimensions as it enables contact-less control of large deformations, which can hardly be achieved by other actuation principles in small space. Two different approaches are being pursued to develop ferromagnetic shape memory (FSMA) microactuators based on the magnetically induced reorientation of martensite variants: (1) the fabrication of free-standing epitaxial Ni-Mn-Ga thin film actuators in a bottom-up manner by magnetron sputtering, substrate release and integration technologies and (2) the top-down approach of thickness reduction of bulk Ni-Mn-Ga single crystals to foil specimens of decreasing thicknesses (200 -40 µm) and subsequent integration. This review describes the fabrication technologies, procedures for thermo-mechanical training adapted to the quasi-two-dimensional geometries of film and foil specimens as well as the performance characteristics of state-of-the art actuators after processing and training.
Abstract. The coupled magnetic and mechanical properties of single crystalline Ni-Mn-Ga foil actuators are investigated for decreasing thicknesses in the range from 200 6 The foils exhibit a narrow martensitic phase transformation above room temperature below the Curie temperature of 369 K. Single crystalline Ni-Mn-Ga beam actuators are fabricated by laser micromachining. As-prepared specimens show enlarged twinning stress and thus no measurable magneto strain. Therefore, several training methods are adapted to the quasi-two-dimensional geometry of the foils. As compression training can no longer be applied in lateral direction of thin foils, more sophisticated magneto-thermo-mechanical treatments are required. We show that the low twinning stress of the bulk reference specimens can be recovered. Magnetization experiments and the direct observation of magneto strain on trained foil actuators show different degrees of reorientation up to 1% depending on the training method. The observed partial reorientation effect is discussed in terms of the foil geometry and training parameters.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.