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HL: Halbleiterphysik

HL 33: II-VI Halbleiter I

HL 33.3: Vortrag

Mittwoch, 26. März 2003, 16:45–17:00, BEY/118

Exchange interactions in narrow-gap Hg_1−xMn_xTe magnetic 2DEG — •J. Liu, Y. S. Gui, V. Daumer, K. Ortner, V. Hock, C. R. Becker, H. Buhmann, and L. W. Molenmkamp — Physikalisches Institut der Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

In magnetic 2DEG (M2DEG) systems, there exist two classes of exchange interactions: the sp-d exchange interaction between the magnetic ions and the band electrons, and the antiferromagnetic spin-spin exchange interaction between the d-electrons of the magnetic ions. Here, we present the results of studies on two exchange interactions in narrow-gap Hg_1−xMn_xTe M2DESGs by using low temperature magnetotransport measurements. sp-d exchange interaction induces a giant Zeeman splitting through a temperature and magnetic field dependent effective g-factor, g^*; g^* modulates the amplitude of the Shubnikov-de Haas (SdH) oscillations according to cos(πυ), with υ= δ /(ℏ ω_c). By analyzing the temperature dependent beating patterns, the saturated spin splitting energy E_max relating to sp-d exchange interaction and the antiferromagnetic temperature T₀ relating to the spin-spin interaction, were extracted. Both two parameters exhibit higher values compared with the bulk samples, which indicates the enhanced exchange interactions in a reduced dimensionality. The sp-d exchange interaction can be enhanced due to more isolated Mn spins near the barrier/well interface[1]; the enhancement of super-exchange interaction is possibly resulting from the hybridization mechanism in low dimensional systems.

[1] W. Ossau and B. Kuhn-Heinrich, Physica B 184, 422 (1996).