Spin ordering in semiconductor heterostructures with ferromagnetic δ layers

We report on theoretical study of the magnetic properties of a magnetic metal delta layer embedded into a nonmagnetic nondegenerated semiconductor, taking into account the diffusion smearing, that is unavoidable in the case of delta doping. The system of interest is modeled by the delta layer core, enriched in metal atoms, and a nearly depleted smeared periphery. Confinement states in the form of two-dimensional spin-polarized subbands within the semiconductor band gap arise from potential and exchange scattering of carriers at the core. The mechanism of indirect exchange between impurity spins placed within the peripheral region of the delta layer, via partially occupied confinement states, is analyzed. It is shown that, in the case of a ferromagnetic core, the impurity spins align parallel or antiparallel to the core magnetization, due to the polarization of carriers in the confinement states. Allowing for the confinement mechanism of interaction between the impurity spins as well as for the exchange mechanism through deep levels of the semiconductor host, the magnetic configuration of the impurity spins in the peripheral region of the delta layer is obtained in the framework of a phenomenological approach.