  In this paper, we discuss spin transport in topological insulator (TI) and
diluted magnetic semiconductor (DMS) heterogeneous structures. In DMS / FM
(Ferromagnetic Metal) heterogeneous structure, the spin injection efficiency
changes according to the electric field and Fermi energy were investigated. The
higher electric field, the stronger spin injection efficiency, and its velocity
of increase gets lower and approaches to the equilibrium state. Additionally,
the higher interface conductivity, the weaker spin injection efficiency, and
the transmission due to Fermi energy of spin up and spin down is different from
each other. In the same structure, the spin injection efficiency changes
depending on the magnetic field, and the spin injection efficiency vibrates
sensitively according to the magnetic field. In TI / DMS heterogeneous
structure, the spin current changes according to magnetic field were
investigated. Here, when the magnetic field is low, the spin current
oscillates, and as the magnetic field increases, the vibration is attenuated.
It also decreases with increasing temperature and weakens vibrations. This is
due to the competitive effect of the chiral properties of Dirac type
quasiparticles in the topological insulator and the unique properties of
exchange interaction between electrons and ions in DMS. This result allows us
to expect the possibility of spintronic devices with high sensitivity to
magnetic field.
