  In multiferroic oxides with a transverse helical magnetic order, the
magnetization exchange coupling is sinusoidally space-dependent. We
theoretically investigate the spin-dependent electron grating effect in
normal-metal/helical-multiferroic/ferromagnettic heterojunctions. The spin wave
vector of the spiral can be added or subtracted from the electron spacial wave
vector inducing spin-conserved and spin-flipped diffracted transmission and
reflection. The predicted grating effect can be controlled by magnetization
exchange coupling strength, the helicity spatial period, and the magnetization
of the ferromagnetic layer.
