  A numerical investigation is conducted for a single spin-torque oscillator
under the non-linear region. A large angle precession triggers the generation
of multiple modes without any feedbacked circuits and/or magnetic couplings
with neighboring oscillators. Our simulations show that a single eigenmode of a
given spin-torque oscillator can trigger up to six discrete modes as the
sideband modes. These findings will offer the new functionality to the STO for
developing the spintronic logic circuits.
