Polycrystalline Sense Layer for Magnetic Tunnel Junction (MTJ) as Ultrasensitive Sensing Element for MEMS Pressure Sensors

This paper reports Magnetic Tunnel Junctions (MTJ) based spintronic MEMS pressure sensor with polycrystalline magnetostrictive sense layer producing huge gauge factor. This layer of the MTJ converts the stress into the magnetic polarization. The trade-off between ferromagnetic behavior of polycrystalline thin films and magnetostriction is addressed for the first time in a MEMS pressure sensor. The sense layer behavior for MTJ with 1nm thick MgO tunnel barrier sandwiched between CoFeB thin films is discussed. TMR value is much more than 200% for polycrystalline sense layers and the analytical model shows how the increase in TMR value increases the gauge factor to 3406 in a range of 600 mbar pressure.