  In this note, we study the effects of non-zero magnetic field on the fermion
spectral function coupled with a non-minimal coupling in the background of a
dyonic $AdS_4$ black hole. The system can be reduced to a non magnetic one with
the momentum being quantized into Landau levels $n$. By tuning the coupling
parameter, we study its effect on the Fermi level and the quasiparticle width.
We found an interesting scaling relation between the decay width and the
coupling parameter, with a universal scaling exponent which is independent of
the levels $n$.
