  We theoretically study magnetic field, temperature, and energy band-gap
dependences of magnetizations in the Dirac fermions. We use the zeta function
regularization to obtain analytical expressions of thermodynamic potential,
from which the magnetization of graphene for strong field/low temperature and
weak field/high temperature limits are calculated. Further, we generalize the
result by considering the effects of impurity on orbital susceptibility of
graphene. In particular, we show that in the presence of impurity, the
susceptibility follows a scaling law which can be approximated by the Faddeeva
function. In the case of the massive Dirac fermions, we show that a large
band-gap gives a robust magnetization with respect to temperature and impurity.
In the doped Dirac fermion, we discuss the dependence of the band-gap on the
period and amplitude of the de Haas-van Alphen effect.
