  The hole distribution in a double quantum well (QW) structure consisting of a
magnetic and a nonmagnetic semiconductor QW is investigated as a function of
temperature, the energy shift between the QWs, and other relevant parameters.
When the itinerant holes mediate the ferromagnetic ordering, it is shown that a
bistable state can be formed through hole redistribution, resulting in a
significant change in the properties of the constituting magnetic QW (i.e., the
paramagnetic-ferromagnetic transition). The model calculation also indicates a
large window in the system parameter space where the bistability is possible.
Hence, this structure could form the basis of a stable memory element that may
be scaled down to a few hole regime.
