  The effect of the Zeeman field on the defect-induced Kondo effect in graphene
is investigated. The effective model of the Kondo effect is derived, and is
analyzed on the basis of the numerical renormalization group method. It is
found that, under the Zeeman field, at the border of the spin polarized state
and the Kondo-Yosida singlet state, there is an unusual fixed point where the
entropy of the defect is k_B ln2 and the expectation value of S^2_z is 1/8.
