  To one loop the effective neutrino photon interaction takes place through the
vector-vector type and the axialvector-vector type amplitude. In this work we
explicitly write down the form of the axialvector-vector amplitude to all
orders in the external magnetic field in a medium. We then infer upon its zero
external momentum limit which contributes to the effective charge of the
neutrinos inside a magnetized medium. We further show its gauge invariance
properties.
