  Imaging of structural defects in a material can be realized with a
radio-frequency atomic magnetometer by monitoring the material's response to a
radio-frequency excitation field. We demonstrate two measurement configurations
that enable the increase of the amplitude and phase contrast in images that
represent a structural defect in highly electrically conductive and high
magnetic permeability samples. Both concepts involve the elimination of the
excitation field component, orthogonal to the sample surface, from the atomic
magnetometer signal. The first method relies on the implementation of a set of
coils that directly compensates the excitation field component in the
magnetometer signal. The second takes advantage of the fact that the
radio-frequency magnetometer is not sensitive to the magnetic field oscillating
along one of its axes. Results from simple modelling confirm the experimental
observation and are discussed in detail.
