Seminários

Diluted magnetic semiconductors - our understanding from ab-initio theory

Biplab Sanyal
Department of Physics and Astronomy, Uppsala University, Sweden


The understanding of diluted magnetic semiconductors (DMS), the essential materials for semiconductor spintronics is still quite inadequate even after several years of extensive experimental and theoretical research. The conflicting experimental results obtained under different conditions have led us to infer about the presence of inhomogeneities in the samples in the form of clustering of dopants, formation of secondary phases etc. Though Mn doped GaAs, a prototype for III-V DMS is understood in quite detail, II-VI oxide based DMS have been quite mysterious. The initial theoretical prediction of high temperature DMS has not been achieved indisputably. In this talk, I will present our activities towards the understanding of oxide based DMS. It will be shown that a proper theoretical treatment of homogeneous DMS can never show high transition temperatures and hence Dietl et al.'s prediction of high Tc and hole mediated ferromagnetism should be reconsidered. I will show how defects play important role in controlling the magnetic interactions. Finally, I will present the results of atomistic spin dynamics in Mn doped GaAs to show that the magnetic frustration in presence of compensating donor defects may lead to a slow dynamics in this system.

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