  First-principles techniques are used to investigate the behavior of
BiFeO$_{3}$/LaFeO$_{3}$ perovskite oxide superlattices epitaxially grown on a
(001)-SrTiO$_3$ substrate. The calculations show that 1/1 superlattices exhibit
a $Pmc2_1$ ground state combining a trilinear coupling of one polar and two
oxygen rotational lattice modes, and weak ferromagnetism. The microscopic
mechanism allowing one to manipulate the magnetization with an electric field
in such systems is presented and its dependence on strain and chemical
substitution is discussed. BiFeO$_{3}$/LaFeO$_{3}$ artificial superlattices
appear to be good candidates to achieve electric switching of magnetization at
room temperature.
