A Pd/Co double layer has been grown epitaxially in ultrahigh vacuum on a Pd(111) single crystal, with the Co in the shape of a wedge of thickness varying from 0 to 10 monolayers (ML). The polar magneto‐optical Kerr effect has been used to make a nearly continuous set of measurements of the magnetic properties as a function of Co thicknesstCo. The coercive fieldsHcand nucleation fieldsHnshow large, well‐defined maxima attCo∼2.3 ML. Between 4 and 9 ML, we find thatHcfalls with increasing thickness according to atCo−5/2dependence. The Kerr ellipticity and Kerr rotation depend linearly on Co thickness above ∼2 ML Co, but show appreciable offsets when extrapolated totCo=0. These offsets are clear evidence of the polarization of Pd near the interfaces. Extensiveinsitugrowth studies of the structure of the films are also reported.