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Wide band gap semiconductors as spintronic and ferromagnetic materials

Tomasz Dietl 

Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
Japan Science and Technology Agency, Semiconductor Spintronics Project (ERATO), al. Lotników 32/46, Warszawa 02-668, Poland


In the recent years a considerable effort has been devoted to understand the nature of carrier-controlled ferromagnetism in tetrahedrally coordinated diluted magnetic semiconductors. In these materials conceptual difficulties of charge transfer insulators and strongly correlated disordered metals are combined with intricate properties of heavily doped semiconductors, such as Anderson-Mott localization and defect creation by self-compensation mechanisms. Nevertheless, I will argue that (Ga,Mn)As and related compounds have become the best understood ferromagnets. In particular, the theory built on Zener's model of ferromagnetism and the Kohn-Luttinger kp theory of semiconductors describes quantitatively the thermodynamic, micromagnetic, optical, and transport properties of these systems. Moreover, the understanding of these materials has provided a basis for the development of novel methods enabling magnetisation manipulation and switching. In the context of spintronics, however, especially promising are the group III nitrides and group II oxides. In these systems, the short bond length results in a strong hybridisation between valence band states and open d shells of transition metal impurities, which is predicted to enhance the Curie temperature of the hole-mediated ferromagnetism. While spontaneous magnetisation persisting above room temperature has been detected for a number of magnetically doped nitrides and oxides, we are still at the beginning of the road to understanding and controlling doping, defects, and magnetism of these systems. A review of pertinent experimental results will be presented together with models put forward for their interpretation. The work was partly supported by AMORE and FENIKS EC projects, by Humboldt Foundation, and carried out in collaboration with M. Sawicki, P. Kossacki, and T. Andrearczyk in Warsaw, as well as with groups of H. Ohno, J. Cibert, B. Gallagher, and A.H. MacDonald (a review: MRS Bulletin, October 2003, p. 714)


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Presentation: invited oral at E-MRS Fall Meeting 2004, Plenary session, by Tomasz Dietl
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-05-16 22:29
Revised:   2009-06-08 12:55