Magnetic sensors based on piezoelectric–magnetostrictive composites

Magnetoelectric (ME) composites have been fabricated by sandwiching a lead titanate (PZT) laminate between two magnetostrictive (Tb(Fe0.55Co0.45)1.5) (known as Terfecohan) films. Giant ME effect at low fields obtained is associated to large magnetostriction as well as high magnetostrictive susceptibility of the Terfecohan films. Magnetoelectric voltage coefficients, αE = (∂E/∂H), as large as 3350 and 9650 V m/kA m were achieved, respectively, for the as-deposited, and annealed films. The coefficient αE was, however, highly dependent on the direction of the magnetic field with respect to the electrical polarization. On the basic of this magnetoelectric composite, a magnetic sensor operating in an ac magnetic field of 0.1 mT at a resonant frequency of 40 Hz has been prepared. The ME voltage response in applied magnetic fields (dVME/dH) as large as 130 mV/mT was obtained.