  The oscillating frequency of typical Spin Torque Nano Oscillators (STNOs) can
be modulated by injected DC current or bias magnetic field. And phase locking
of STNOs to an external Radio Frequency (RF) signal can be imposed by AC
current or RF bias magnetic field. However, in this study, we have proposed a
Voltage Controlled Spin Oscillators (VCSOs) by introducing Voltage Controlled
Magnetic Anisotropy (VCMA) effect. The oscillating frequency of VCSOs can be
modulated by VCMA voltage as well as injected DC current. Furthermore, we have
shown a novel locking mechanism caused by AC VCMA voltage. Both the frequency
modulation and voltage locking mechanism are analyzed theoretically by
Nonlinear Auto-oscillator theory and verified by numerical simulation. At last,
we proposed that by utilizing negative capacitance material to enhance VCMA
effect, the locking range for voltage locking can be expanded thus may lead to
easy mutual synchronization of multiple VCSOs.
