  Within the framework of macroscopic quantum electrodynamics in linear, causal
media, we study the van der Waals potentials of ground-state atoms in planar
magnetodielectric host media. Our investigation extends earlier ones in two
aspects: It allows for the atom to be embedded in a medium, thus covers many
more realistic systems; and it takes account of the local-field correction.
Two- and three-layer configurations are treated in detail both analytically and
numerically. It is shown that an interplay of electric and magnetic properties
in neighbouring media may give rise to potential wells or walls. Local-field
corrections as high as 80% are found. By calculating the full potential
including the translationally invariant and variant parts, we propose a way to
estimate the (finite) value of the dispersion potential at the surface between
two media. Connection with earlier work intended for biological applications is
established.
