Preparation, characterization and spin-polarized tunneling studies on evaporated NiMnSb thin films
Thesis/Dissertation
·
OSTI ID:7167202
NiMnSb is an intermetallic ternary compound with a C1[sub b] crystal structure. Most interestingly this magnetic compound exhibits both metallic and semiconducting characteristics at the same time. This results in a 100% spin polarization of the conduction carriers at the Fermi level and the compound is called a [open quotes]half-metallic ferromagnet.[close quotes] This study identifies the optimum conditions required to prepare high quality thin films of this compound by vacuum co-evaporation of three elements. Structural and magnetic characteristics of these films are found to be in good agreement with those reported in the literature for bulk NiMnSb. Hall effect measurements confirm holes (from the antimony-5p band) to be the dominant carriers, as predicted by band calculations. Evidence of half-metallic ferromagnetism is seen in transport studies done on these films. The spin-polarized tunneling technique is employed to estimate the degree of spin polarization of conduction carriers and the extent of half-metallic ferromagnetic nature in this compound. NiMnSb/Al[sub 2]O[sub 3]/Al tunnel junctions are prepared on well characterized NiMnSb compound films. For comparison a set of control junctions are also fabricated on NiMnSb alloy films deposited at room temperatures. The impact of magnetic film surface topography and surface composition, which is dependent on deposition conditions, on the top superconducting Al electrode is evaluated by analyzing the tunnel conductance data. The top Al film in both cases exhibits similar behavior, i.e., critical temperature and critical magnetic field values in the expected range, as well as low spin-orbit scattering. However, a superconducting Al film on an ordered NiMnSb compound displays no clear Zeeman splitting, whereas splitting is observed for superconducting Al film on NiMnSb alloy.
- Research Organization:
- Tufts Univ., Medford, MA (United States)
- OSTI ID:
- 7167202
- Country of Publication:
- United States
- Language:
- English
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