Diluted Magnetic Semiconductor Nanocrystals in Glass Matrix

Abstract

Diluted magnetic semiconductor (DMS), are semiconductors in which a magnetic impurity is intentionally introduced; a small fraction of the native atoms in the hosting non-magnetic semiconductor material is replaced by magnetic atoms. The main characteristic of this new class of compounds is the possibility of the onset of an exchange interaction between the hosting electronic subsystem and electrons originating from the partially-filled d or f levels of the introduced magnetic atom (Erwin et al., 2005; Norris et al., 2008). Once that onset is reached in the above-mentioned exchange interaction, it enables the control of both the electronic, and the optical properties of the end material, using external fields in regimes hardly achieved with other classes of materials. Slightly transitions in metal-doped II-VI and IV-VI semiconductor, as for instance, Cd1-xMnxS, Pb1-xMnxS, and Pb1-xMnxSe, is a typical diluted magnetic semiconductor, in which a small amount of Mn2+ is substitutionally incorporated into the hosting CdS, PbS and PbSe semiconductor crystal structure (Ji et al., 2003; Silva et al., 2007; Dantas et al., 2008; Dantas et al., 2009). Quantum confinement effects can be considered with the incorporating of magnetic ions in semiconductors NCs, modifying the optical, magnetic, and electronic properties in relationship to semiconductor bulk. The transition metal ion (Mn2+) d-electrons, usually located in the band gap region of the hosting semiconductor, are available to promote exchange interactions to the sp-band electrons of the hosting semiconductor (Fudyna, 1988). The sp-d exchange interaction taking place in II-VI, and IV-VI DMS (as for instance in Cd1-xMnxS, Pb1-xMnxS and Pb1-xMnxSe) provides a unique interplay between optical properties and magnetism, which could be strongly-dependent upon the doping mole fraction (x) (Silva et al., 2007; Dantas et al., 2008; Dantas et al., 2009). By varying the material’s doping profile (x) a fine tuning of the semiconductor band gap energy can be achieved. Furthermore, quantum size effects caused by the shrinking in DMS bulk II-VI and IV-VI, as in nanosized particles, enhance the optical and the magnetic properties, even further. In addition, in the presence of applied magnetic fields the sp-d interaction involving electrons, holes, and the hosted magnetic ions is affected, as a result modifying the DMS properties and providing the material basis for new applications in magneto-optical, 6