  In this comment, by using Monte Carlo simulation, we show that the
perpendicular shift of hysteresis loops reported in the commented work is
nothing special but simply due to the fact that the range of field does not
surpass the reversible field beyond which the two branches of the loop merge.
If the reversible field is exceeded, the shift is no longer observed. Moreover,
we point out that even using a small range of field, the shift will not be
observed if the observation time is long enough for the reversible field to
drop within the range.
