  The electromagnetic field inside a cubic cavity filled up with a linear
magnetodielectric medium and in the presence of external charges is quantized
by modelling the magnetodielectric medium with two independent quantum fields.
Electric and magnetic polarization densities of the medium are defined in terms
of the ladder operators of the medium and eigenmodes of the cavity. Maxwell and
constitutive equations of the medium together with the equation of motion of
the charged particles have been obtained from the Heisenberg equations using a
minimal coupling scheme. Spontaneous emission of a two level atom embedded in a
magnetodielectric medium is calculated in terms of electric and magnetic
susceptibilities of the medium and the Green function of the cubic cavity as an
application of the model.
