Low energy electron-magnon states localized at the surface of a ferromagnetic semiconductor

Low-energy surface states are studied which belong to the magnetic-polaron type. These states occur in the spectrum of a ferromagnetic semiconductor for positive s-d exchange integrals in the volume of the system and negative at the surface. Using the Jacobian matrix method we calculate the energy of the localized states and construct the corresponding wave functions. We also find the average values of the z projections of the electron spin, and of the total spin of the surface layer of atoms in these states. It is shown that these states affect the magnetic ordering of the surface by lowering its magnetization, and also lead to mainly antiparallel orientation of the electron spin at the surface of the system relative to the spontaneous moment of the lattice.

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