Transition Metal and Rare Earth Doped Sb2Te3 and Bi2Te3 Diluted Magnetic Semiconductors

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Technical: This project seeks new knowledge and greater understanding of the ferromagnetic state in Sb2Te3 and Bi2Te3. Little is known about the magnetic properties upon doping these materials. The approach of this project is to investigate: (i) the upper limits of incorporation of transition metal (TM) magnetic impurities in thin films of Sb2Te3 and Bi2Te3, (ii) the nature of the TM impurity centers in the host lattice, and (iii) the influence of charge carrier density on the magnetic state of the structure. Ultrafast spin dynamics studies will be used to assess fundamental interaction parameters such as the exchange integrals Jsp,d and Jd,d that govern the coupling energy between the TM ions and carriers, and between TM ions themselves. Additionally, studies of the influence of rare earths and their partially filled f-orbitals on stimulating magnetic interactions in Sb2Te3 and Bi2Te3 will be explored. It is expected, that since the orbital moment is not quenched, the s, p-f exchange interactions may be stronger which could lead to higher Curie temperature provided enough of the rare earth ions can be incorporated in the thin film matrix and antiferromagnetic superexchange is not too strong. Non-Technical: The project addresses basic research issues in a topical area of materials science having high technological relevance. The research will contribute basic materials science knowledge at a fundamental level to new understanding and capabilities for potential next generation electronic/spintronic devices. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. The project provides a rich training ground (MBE growth, structural, transport, and magnetic characterization) for graduate and undergraduate students in areas that have technological significance. Aspects of this research are presented to graduate students as part of regularly scheduled colloquia and the topic of spintronics is incorporated to enliven the curriculum of an introductory physics course. The project is cofunded by the DMR Electronic Materials and Condensed Matter Physics Programs.