We have investigated the magnetic properties of an array of holes in an Fe
film using the magneto-optic Kerr effect. We develop the theory of diffract
ion from an array to include magneto-optic effects. The theory allows us to
interpret the differences in the magnetic loops observed on the reflected
beam and those observed on diffracted spots. The latter contain more detail
ed information on the magnetic structure in the vicinity of the holes and a
llow us to infer differences in the switching mechanism for fields applied
along the easy and hard axes. [S0163-1829(99)01509-X].