Magnetic-Field-Induced Reorientation in Single Crystalline Ni-Mn-Ga Foil Actuators

Abstract

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.

Effects of Surface Pinning, Locking and Adaption of Twins on the Performance of Magnetic Shape-Memory Alloys

“…Refs. [13][14][15][16][17]). The lack of repeatability and insufficient resistance against fatigue damage are still hindering commercialization of MSMA technology.…”

A novel foil actuator using the magnetic shape memory effect

“…So far, however, no MSM microactuator based on an epitaxial thin film has been demonstrated. An alternative approach is ferromagnetic shape memory foils, which are fabricated by thinning of bulk single crystals showing ferromagnetic shape memory behavior [8][9][10]. In this case, the technological challenges are related to the minimization of surface defects created during foil fabrication.…”