Wireless and passive temperature indicator utilizing the large hysteresis of magnetic shape memory alloys

An ultra-low cost, wireless magnetoelastic temperature indicator is presented. It comprises a magnetostrictive amorphous ribbon, a Ni-Mn-Sn-Co magnetic shape memory alloy with a highly tunable transformation temperature, and a bias magnet. It allows to remotely detect irreversible changes due to transgressions of upper or lower temperature thresholds. Therefore, the proposed temperature indicator is particularly suitable for monitoring the temperature-controlled supply chain of, e.g., deep frozen and chilled food or pharmaceuticals. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4739836]