  Frequency dependence of magnetoelectric (ME) coupling is investigated in
trilayers of ferromagnetic alloy and piezoelectric lead zirconate titanate
(PZT). The ferromagnetic phases studied include permendur, a soft magnet with
high magnetostriction, iron, nickel, and cobalt. Low frequency data on ME
voltage coefficient versus bias magnetic field indicate strong coupling only
for trilayers with permendure or Ni. Measurements of frequency dependence of ME
voltage reveal a giant ME coupling at electromechanical resonance. The ME
interactions for transverse fields is an order of magnitude stronger than for
longitudinal fields. The maximum voltage coefficient of 90 V/cm Oe at resonance
is measured for samples with nickel or permendure and is three orders of
magnitude higher than low-frequency values.
