High field magnetotransport and point contact Andreev reflection measurements on CuCr_2Se_4 and CuCr_2Se_3Br-Degenerate magnetic semiconductor single crystals

摘要

Single crystals of the metallically degenerate fully magnetic semiconductors CuCr_2Se_4 and CuCr_2Se_3Br have been prepared by the Chemical Vapour Transport method, using either Se or Br as transport agents. The high-quality, millimetre-sized, octahedrally faceted, needle- and platelet-shaped crystals are characterised by means of high field magnetotransport (μ_0H ≤ 14 T) and Point Contact Andreev Reflection. The relatively high spin polarisation observed |P| > 0.56, together with the relatively low minority carrier effective mass of 0.25 m_e, and long scattering time 10~(-13) s, could poise these materials for integration in low- and close-to-room temperature minority injection bipolar heterojunction transistor demonstrations.