Magneto-transporte e ferromagnetismo Hall em heteroestruturas semicondutoras magnéticas [thesis]

Henrique Jota de Paula Freire
Digital magnetic heterostructures (DMHs) are semiconductor structures with magnetic impurities (Mn) restricted to some planar arrangements (monolayers) regularly spaced. In the presence of an external magnetic eld, the sp-d exchange interaction between the localized magnetic moments and the itinerant carriers is responsible for a giant spin splitting, of the order of, or even greater than, the cyclotron separation between Landau levels. Here I calculate the electronic structure of group II-VI
more » ... gital magnetic quantum wells. I solve the Kohn-Sham equations of the spin-density functional theory within the eective mass approximation. Then I calculate some magneto-optical and transport properties which are experimentally relevant. In particular, I investigate the spin dependent physics of these systems from two dierent points of view. First, I focus on eects of the Mn magnetism on the sp-d exchange spin dependent potential, particularly the eect of antiferromagnetic clustering and the eect of dilution (segregation and interdiusion) of the Mn content prole. By considering these eects I reproduce experimental results for the spin splitting ∆E and spin scattering times τ sf [S. A. Crooker et al., Phys. Rev. Lett. 75, 505 (1995); Phys. Rev. B 61, 1736 (2000)]. In the second part I move on to the physics of spin-polarized two-dimensional electron gases (2DEGs), and show the relevance of the strong dependence of the many-body contributions (exchange and correlation) with the spin polarization. In particular, these eects are relevant for the development of quantum Hall ferromagnetic phases. I calculate magnetotransport in the quantum Hall eect regime for DMHs consisting of ZnSe and CdTe. My results reproduce experimental results [R. Knobel et al., Phys. Rev. B 65, 235327 (2002); J. Jaroszy«ski et al., Phys. Rev. Lett. 89, 266802 (2002)] for the dependence with magnetic eld, temperature, development of anomalous resistivities spikes and hysteretic behaviors in many physical properties. xi
doi:10.11606/t.76.2004.tde-23032007-183322 fatcat:eunbyu7hrbelppn2zr6ngfj4aq