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−xMn xAs M S with x = 1/32, a nonmagnetic I with a realistic dimension, and a H g Ba 2 Ca 2 Cu 3 O 8.4 (Hg-1223) high- T c S. The normalized charge and spin currents, Q T , C μ ′ V e x and Q T , S μ ′ V e x , and the flows of the majority ↑ and minority ↓ spin electrons, Q T , ↑ μ ′ V e x and Q T , ↓ μ ′ V e x , have been calculated at a fixed external voltage V ex , as a function of the magnetic moment μ′ ( ≡ μ / μ B ) 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 M S / 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.