FUNCTIONALLY GRADED PIEZOMAGNETIC AND PIEZOELECTRIC BILAYERS FOR MAGNETIC FIELD SENSORS: MAGNETOELECTRIC INTERACTIONS AT LOW- FREQUENCIES AND AT BENDING MODES

摘要

In a piezomagnetic-piezoelectric bilayer the interaction between the magnetic and electric subsystems occurs through mechanical forces. This study is on magneto-electric (ME) interaction in a bilayer of PZT and ferromagnetic layer in which the piezomagnetic coefficient q is graded. The grading is accomplished with the use of Ni (negative q) and Ni-Fe alloy or Permendur (positive q). At low-frequencies the ME coefficient shows a four-fold increase compared to homogeneous Ni-PZT bilayer. Bending resonance and consequent enhancement in ME coupling occurs at the lowest frequency, 800-1200 Hz, for a bilayer that is fixed at one end and free at the other end. The peak ME coefficient at resonance is in the range 12-15 V/cm Oe and is 10% higher for graded samples compared to Ni-PZT. The graded bilayers are promising candidates for use in ultrasensitive magnetic field sensors.