Coupling of the magnetic Sayers and electron spin polarization in four-layer structures of amplitude and nonmagnetic semiconductors

摘要

The electron energy spectrum, the energy E{sub}m of the exchange coupling between magnetic layers, and the relative polarization β of the electron spins in semiconductor structures with two ferromagnetic barriers and nonmagnetic layers acting as potential wells for electrons are considered. For the example of EuS/PbS(001) structures it is shown that in the case of Fermi statistics E{sub}m is a sign-varying oscillatory function of the width a of the potential well between barriers, and with increasing electron density n{sub}0 in the wells and increasing thickness d of the nonmagnetic sublayers between the barrier and substrate, the extrema of E{sub}m are shifted to smaller a and their amplitudes rapidly increase. As the temperature is lowered from the Curie point, the energy E{sub}m, depending on a, n{sub}0, and d, can increase (in modulus) monotonically or nonmonotonically, change sign from positive to negative, or change sign twice. The polarization β decreases with increasing a, n{sub}0, and d, undergoing sharp jumps when E{sub}m changes sign. For Boltzmann statistics only a ferromagnetic orientation of the barrier magnetizations (E{sub}m<0) is possible.