  We investigate the far-infrared (FIR) absorption of a two-dimensional
electron gas in a periodically modulated quantizing magnetic field. The
magnetic field varies along only one spatial direction and the external
time-dependent electric field is linearly polarized along that axis. The mutual
Coulomb interaction of the electrons is treated self-consistently in the ground
state and in the absorption calculation within the Hartree approximation. The
effects of the magnetic material on top of the heterostructure as a grating
coupler is included in the time-dependent incident FIR electric field. We show
that similar to an electric modulation, the absorption can be directly
correlated to the underlying electronic energy bands. In addition, the magnetic
modulation leads to absorption spectra with a richer structure due to the quite
different static response of the electron density to the modulation.
