  It has been demonstrated that a circularly polarized linear down-chirp
microwave field pulse (LDCMWP) reverses a single-domain of high anisotropy
magnetic nanoparticle but not efficient as expected. Therefore, based on the
Landau-Lifshitz-Gilbert equation, we study the nonlinear down-chirp microwave
field pulse (NLDCMWP) driven magnetization reversal, which can induce fast and
energy-efficient reversal since the reversal time is close to the theoretical
limit and the required field amplitude and initial frequency band are smaller
than that of the LDCMWP. The fast and energy-efficient magnetization reversal
is obtained because the frequency change of the NLDCMWP closely matches the
frequency change of the magnetization precession which leads to efficient
stimulated microwave energy absorption (emission) by (from) the magnetic
particle before (after) it crosses over the energy barrier. Moreover, we found
that the enhancement of hard anisotropy reduces the initial frequency band and
the microwave amplitude of NLDCMWP and the material with the larger damping is
better for fast magnetization reversal. These investigations may give a pathway
to realize the fast and energy-efficient magnetization reversal.
