Thermal energy harvesting by high frequency actuation of magnetic shape memory alloy films

A novel energy harvesting device using magnetic shape memory alloy (MSMA) film actuation is presented showing a power density of up to 3 mW/cm³ at a temperature change of the material of about 2 K. This exceeds the power output of previous MSMA harvesting devices by at least three orders of magnitude and challenges state-of-the-art thermoelectrics. The results are accomplished by using a tailored Ni-Co-Mn-Ga film with large temperature-dependent change of magnetization at the Curie temperature T_C and a new cantilever design, with low thermal mass for rapid heat transfer in the order of 10 ms, matching the time constant of eigenoscillation.