  In the framework of Nambu--Jona-Lasinio model beyond mean field
approximation, the effects of pion fluctuations on (inverse) magnetic catalysis
and magnetic susceptibility are studied. The negative magnetic susceptibility
at low temperature is observed when contributions from both neutral and charged
pions are taken into account. In weak field approximation, it is observed that
at finite temperature, the magnetic inhibition effect in the chiral limit,
resulting from the difference between the transverse and longitudinal
velocities of neutral pions, converts to weak magnetic catalysis when
considering a non-zero current quark mass. Moreover, the magnetic catalysis is
amplified by the charged pions.
