CAREER: Spin Polarization Spectroscopy of Complex Magnetic Materials and Spin Electronic Devices

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The possibility of exploiting the spin of electrons (or holes) in electronic devices has led to the emergence of the new field of spintronics. The efficiency of spintronics devices is strongly dependent on the degree of the spin polarization in a ferromagnet. In particular, half-metals, which are 100% spin-polarized, are of fundamental importance for the next-generation of electronic devices. The experimental confirmation of the existence of such highly spin-polarized materials systems is vital to spintronics. The proposed research focuses on developing a fundamental understanding of the basics of spin transport in highly spin-polarized materials and on the ongoing search for novel highly spin-polarized materials.We propose a cohesive research program to further develop and expand Point Contact Andreev Reflection (PCAR) Spectroscopy and to apply it to the spin polarization measurements in dilute magnetic semiconductors and metal alloys. In addition, we propose to explore the viability of a new nonvolatile ferromagnet-superconductor device based on Andreev reflection. The proposal also includes an initial exploratory study of spatially resolved spin polarization measurements (Spin Mapping) with potential in situ capabilities.The PI has recently observed for the first time Andreev reflection in the point contact geometry in a non-magnetic semiconductor, and has obtained some preliminary results in magnetic semiconductors. These results strongly indicate that the PCAR technique can become a viable measurement technique for dilute magnetic semiconductors, which is crucial for the future development of this field. In addition to the spin polarization measurements, transport, magnetic, chemical, and structural analysis will be performed to study in detail the following materials systems: 1) Dilute magnetic and non-magnetic semiconductors: Non-magnetic semiconductors (e.g., BeGaAs). Magnetic semiconductors: GaMnSb, GaMnAs, InMnSb, and MnAs.2)Other theoretically predicted half-metals: double perovskites (Sr2FeMoO6,) and CoxFe1-xS2.As part of the broader impact of his research proposal the PI is planning to promote collaboration with the local industry (especially Delphi Automotive) and with HYPRES (on ferromagnet/superconductor nonvolatile device). He is also collaborating with Oak Ridge National Laboratory, where the PI is one of the "University Champions" of the new Nanophase Materials Science Center. The spatially resolved spin polarization measurements (Spin Mapping) and will be investigated in partnership with the Center.The PI is actively involved in a comprehensive program to broaden participation of minorities in physics. He gives public lectures to high school students to explain what is involved in being a physicist and to try to eliminate a psychological barrier that often prevents many minority students and women from becoming a scientist. He is advising the Detroit Science Center on the content and scientific quality of their physics-related exhibits. The PI's two major educational goals, integrated with his research, are:1)Develop a pilot program aimed at introducing a Senior Research Project at WSU as a required part of the curriculum.2)Develop a new graduate level course "Magnetism, Magnetic Devices and Nanotechnology". This course will introduce the basic concepts in magnetism, GMR and TMR devices and sensors, novel magnetic materials, spin transport and spin polarization measurements, and modern nanofabrication techniques.