Spin Flows in Magnetic Semiconductor/Insulator/Superconductor Tunneling Junction

Tunneling currents along the c-axis of the majority and minority spin electrons have been studied for a magnetic semiconductor (MS)/insulator (I)/superconductor (S) tunneling junction consisting of a Ga1−xMnxAs MS with x = 1/32, a nonmagnetic I with a realistic dimension, and a HgBa2Ca2Cu3O8.4 (Hg-1223) high-Tc S. The normalized charge and spin currents, QT,Cμ′Vex and QT,Sμ′Vex, and the flows of the majority ↑ and minority ↓ spin electrons, QT,↑μ′Vex and QT,↓μ′Vex, have been calculated at a fixed external voltage Vex, as a function of the magnetic moment μ′ (≡μ/μB) per a Mn atom which is deduced from the band structure calculations. It is found that the tunneling due to the minority spin electron dominates when μ′<2.4, but such a phenomenon is not found for μ′>2.4. We have pointed out that the present MS/I/S tunneling junction seems to work as a switching device in which the ↑ and ↓ spin flows can be easily controlled by the external magnetic field.