  We propose and analyze a spin wave amplifier aimed to enhance the amplitude
of the propagating spin wave via the magnetoelectric effect. The amplifier is a
two-layer multiferroic structure, which comprises piezoelectric and
ferromagnetic materials. By applying electric field to the piezoelectric layer,
the stress is produced. In turn, the stress changes the direction of the easy
axis in the ferromagnetic layer and the direction of the anisotropy field. The
rotation frequency of the easy axis is the same as the frequency of the spin
wave propagating through the ferromagnetic layer. As a result of this two-stage
process, the amplitude of the spin wave can be amplified depending on the angle
of the easy axis rotation. We present results of numerical simulations
illustrating the operation of the proposed amplifier. According to numerical
estimates, the amplitude of the spin wave signal can be increased by several
orders of magnitude. The energy efficiency of the electric-to-magnetic power
conversion is discussed. The proposed amplifier preserves the phase of the
initial signal, which is important for application to logic circuits based on
spin waves.
