Spontaneous emission between two parallel plates, one or both infinitely permeable

We compute the influence on the spontaneous-emission rate for a two-level atom when it is located between two parallel plates of a different nature, namely a perfectly conducting plate (epsilon -->infinity) and un infinitely permeable one (mu -->infinity). We also discuss the case of two infinitely permeable plates. We compare our results with those found in the literature for the case of two perfectly conducting plates.