1. Understanding the chemical origins of half-metallic ferromagnetism Ram Seshadri, UC Santa Barbara, DMR-0449354 Research: Half-metallic ferromagnets are a class of magnetic materials with the special quality that all the conduction electrons belong to only one spin direction. Research aimed at understanding at a fundamental chemical level, why some materials and not others show this property is expected to lead to new materials for spin-based electronic devices. Collaborative work with Professor Claudia Felser in the University of Mainz, Germany, suggests that half metals such as the half-Heusler XYZ compounds, display this property because they possess highly directed and covalent chemical bonds. The results of computations, displayed alongside for two compounds, TiCoSb, and VCoSb, indicate these compounds can be thought to comprise a diamond-like semiconducting network. Such understanding has helped predict new candidate half-metals that are currently being investigated using experiments and computation. A manuscript (cond-mat/0509472) is available.(cond-mat/0509472)

2. The figure displays, for two different half-Heusler compounds, the electron localization function, and the electronic charge density. TiCoSb is a semiconductor and VCoSb is a half-metallic ferromagnet. These figures strongly suggest that the Co and Sb atoms form a covalently bonded zinc blende lattice, isostructural and isoelectronic with GaSb. The Ti4+ and V5+ ions are not a part of this covalent network. This analysis permits this class of half-metallic ferromagnets to be thought of as semiconductors stuffed with magnetic ions. Understanding the chemical origins of half-metallic ferromagnetism Ram Seshadri, UC Santa Barbara, DMR-0449354

3. Understanding the chemical origins of half-metallic ferromagnetism Ram Seshadri, UC Santa Barbara, DMR-0449354 Broader impact: In August 2005, the PI co-organized a 2-week Materials Summer School, sponsored by the ICMR program of the National Science Foundation. Apart from a number of students from within the US, the summer school emphasized participation by students from countries that have not traditionally had a strong science infrastructure, eg. countries in South America. The photograph shows the over 50 participants in the quad of UCSB’s new Engineering Sciences building. The PI is in the last row standing second from right.