  We report on the observation of linear and circular magnetogyrotropic
photogalvanic effects in InSb/AlInSb quantum well structures. We show that
intraband (Drude-like) absorption of terahertz radiation in the
heterostructures causes a dc electric current in the presence of an in-plane
magnetic field. The photocurrent behavior upon variation of the magnetic field
strength, temperature and wavelength is studied. We show that at moderate
magnetic fields the photocurrent exhibits a typical linear field dependence. At
high magnetic fields, however, it becomes nonlinear and inverses its sign. The
experimental results are analyzed in terms of the microscopic models based on
asymmetric relaxation of carriers in the momentum space. We demonstrate that
the observed nonlinearity of the photocurrent is caused by the large Zeeman
spin splitting in InSb/AlInSb structures and an interplay of the spin-related
and spin-independent roots of the magnetogyrotropic photogalvanic effect.
