Measurement of spin polarization in p- In0.96Mn0.04As using Andreev reflection spectroscopy

We report on the transport behavior and spin polarization of carriers P for superconductor/ferromagnetic semiconductor (S-F) junctions. We fabricated Nb/ferromagnetic semiconductor p-In0.96Mn0.04As junctions with Hall voltage probes. Below ∼15 K, p- In0.96Mn0.04As becomes ferromagnetic and then the anomalous Hall effect is observed. Below the TC of the Nb electrodes (∼8.2 K), we observed a conductance reduction within the Nb superconducting energy gap voltage owing to the suppression of Andreev reflection by spin polarization in p- In0.96Mn0.04As. We have evaluated the degree of spin polarization in p- In0.96Mn0.04As experimentally by comparing the measured differential conductance with that obtained with the Strijkers model extended for spin-polarized Andreev reflection including the inverse proximity effect. Consequently, the P value extracted experimentally for p- In0.96Mn0.04As at 0.5 K was P=0.33∼0.795.