  The effect of noise on the process of high-speed remagnetization of vortex
state of a pentagonal array of five circular magnetic nanoparticles is studied
by means of computer simulation of Landau-Lifshits model. The mean switching
time and its standard deviation of the reversal between the counterclockwise
and clockwise vorticities have been computed. It has been demonstrated that
with the reversal by the pulse with sinusoidal shape, the optimal pulse
duration exists, which minimizes both the mean switching time (MST) and the
standard deviation (SD). Besides, both MST and SD significantly depend on the
angle between the reversal magnetic field and pentagon edge, and the optimal
angle roughly equals 10 degrees. Also, it is demonstrated that the optimization
of the angle, duration and the amplitude of the driving field leads to
significant decrease of both MST and SD. In particular, for the considered
parameters, the MST can be decreased from 60 ns to 2-3 ns. Such a chain of
magnetic nanoparticles can effectively be used as an element of
magnetoresistive memory, and at the temperature 300K the stable operation of
the element is observed up to rather small size of nanoparticles with the
raduis of 20 nm.
