  Effects of a microwave voltage on magnetization precession are analyzed based
on a macrospin model. The microwave voltage induces the oscillating anisotropy
field through the voltage controlled magnetic anisotropy (VCMA) effect, and
then stimulates the magnetization. The large angle precession is maintained if
the magnetization synchronizes with the microwave voltage. The effective
equations of motion of the magnetization with an oscillating anisotropy field
are derived, and the mechanism of the synchronization is clarified by analyzing
the derived equations of motion. The conditions of the angular frequency
detuning and the amplitude of the oscillating anisotropy field for
synchronization are obtained. The results are useful for development of the
VCMA-based energy-efficient spintronics devices using magnetization precession
such as a VCMA-based magnetoresistive random access memory and a nano-scale
microwave magnetic field generator.
