Ph.D. Thesis Defence

Candidate: A. Rajanikanth
Title: Spin polarization measurements of Heusler alloys by the point contact
Andreev reflection method

Supervisor: K. Hono, Professor
Committee: S. Uji, Professor
E. Kita, Professor
H. Asano, Professor (Nagoya Univ.)

Date: June 22, 2007
Time: 15:00 - 17:00
Place: Sengen, 8th foor seminar room (#812)

Abstract:
Materials with 100% spin polarization are required for realizing spintronics devices for practical applications. Point contact Andreev reflection (PCAR) is the easiest and most practical technique to measure the spin polarization of materials. Following the expeirmental descriptions on spin polarization measurements by PCAR, the way to engineer the materials for realizing high spin polarization in Heusler alloys will be discussed. Spin polarization of ternary Heusler alloys with X2YZ composition, which are theoretically predicted to possess 100% spin polarization near the Fermi level, have been measured. PCAR measurements estimatd 60% spin polarization for Co2MnSn, which is one of the highest values among the ternary Heusler alloys measured by PCAR. Substitution of Al for Sn lead to two phase alloys composed of Al and Sn rich phases, the spin polarization of which was found to be higher than the single phase allooy, 63%. Further enhancement of spin polarization was found by substituting Fe for Mn, 65% for Co2Mn0.95Fe0.05Sn. These reults are discussed based on recent ab-initio calculation results.