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Presents an analysis of both deep level transient spectroscopy and transient microwave absorption spectroscopy for the case of DX centers in AlGaAs. Experimental details; Discussion; Conclusions.

ESR experiments from PtRhRe grown and highly semiconductor-metal separated single-walled carbon nanotubes (SWCNTs) were performed at 9.45 GHz and temperatures T between 0.39 and 200 K. No explicit evidence was found for a response from itinerant electrons in the metallic tubes. Rather, in both the metallic (M) and the semiconducting (SC) tubes, the ESR signal originates from quasi-localized defect spins but interactions with free electrons render the two systems characteristically different. The spin susceptibility was of Curie-Weiss type for T ≥ 10 K. For annealed samples it drops for lower T indicating a transition to a ferromagnetic state. Linewidths decrease and increase with increasing T for M and SC tubes, respectively. As a consequence they cross for the two systems. Interaction of spins with free carriers in M tubes via an RKKY type mechanism and increase of linewidth with temperature for SC tubes due to spin-lattice interaction is suggested to be responsible for this. [ABSTRACT FROM AUTHOR] more...

Electron spin resonance of a two-dimensional electron gas in an asymmetric silicon quantum well has been investigated. Applying a small de current, we observe a shift in the resonance field due to the additional, current induced Bychkov-Rashba type of spin orbit field. We also show that a high frequency current may induce electric dipole spin resonance very efficiently. [ABSTRACT FROM AUTHOR] more...

In the last years, spin effects in semiconductors have been of great interest not only in the context of solid state physics, but also for their potential use in technology. In this paper, we give a short review of spintronic materials, in which electron spin is exploited as an additional degree of freedom. Afterwards, we discuss the properties of classic, non-magnetic semiconductors, where efforts are put into enriching traditional semiconductor technology by engaging the electrical effects of spin effects. Various phenomena and scientific state of the art is highlighted. [ABSTRACT FROM AUTHOR] more...

This paper is an attempt to modify the classic Ruderman-Kittel-Kasuya-Yosida (RKKY) model to allow the analysis Of the experimental data of the magnetic resonance measurements. In our calculations, we follow the treatment of the original authors of the RKKY model but include the finite band splitting, Δ, as a phenomenological parameter. The RKKY exchange is not anymore of the Heisenberg type and an anisotropy induced by the direction of carrier magnetization occurs. [ABSTRACT FROM AUTHOR] more...

Using ESR, we investigate g-factor and spin coherence time τ of electrons confined in 2D Si1− xGe x {channels} ( x < 0.1) by barriers with x > 0.2 and in SiGe quantum dots grown on prepatterned Si substrates. The quantum wells exhibit 2D-anisotropy of both g and τ which can be explained in terms of the Bychkov–Rashba field. The latter increases with increasing Ge content in the well indicating that the increasing spin-orbit coupling is more important than interface properties. The narrow ESR permits selective spin manipulation already for x > 0.02. Large, regular arrays of Ge quantum dots (about 109) were grown on prepatterned substrates. Strain in the Si capping layer lowers the conduction band relative to that of Ge causing confinement. The g-shift observed implies the possibility of g-tuning by confinement. The line width shows substantial inhomogeneous broadening whereas the longitudinal spin lifetime is hardly changed with respect to 2D structures. [ABSTRACT FROM AUTHOR] more...

Electrical transport measurements are reported on 2-DEG in a CdMnTe quantum well structure. At low magnetic fields the Shubnikov-de Haas oscillations show a beating pattern with nodes which are a direct consequence of the large Pauli paramagnetism. The effective electron Zeeman splitting (EZ) has been tuned via the s-d exchange interaction in order to probe the quantum Hall effect under conditions of vanishing Zeeman energy. We have observed that reducing EZ to zero does not necessary imply a closing of the spin gap. [ABSTRACT FROM AUTHOR] more...

We investigate the electron spin resonance of electrons in Si1-xGex quantum wells defined by SiGe barriers (19%–25%Ge). Adding small amounts of Ge changes both g-factor and linewidth and their anisotropy. We explain these effects in terms of the Bychkov–Rashba field that originates from one-sided modulation doping. The main effect arises from the increase in spin–orbit interaction with increasing x. We argue that these effects may be used to tune the g-factor of electrons in quantum dots for a selective spin manipulation. [ABSTRACT FROM AUTHOR] more...

Electron spin resonance of two-dimensional (2D) electron gas in Si/SiGe quantum wells allows to evaluate both the longitudinal and the dephasing spin relaxation time. Diakonov–Perel (DP) relaxation, caused by Bychkov–Rashba (BR) spin orbit coupling, occurs to be the dominant mechanism in high mobility samples. For low mobility the Elliott–Yaffet mechanism dominates the longitudinal spin relaxation. When the BR effect is small, inhomogeneous broadening caused by potential fluctuations is seen. We compare spin relaxation of the 2D electron gas in Si and in GaAs quantum wells with respect to applications of these materials in spintronics. [ABSTRACT FROM AUTHOR] more...

MBE grown Ga1− xMn xAs layers were investigated by means of magnetic resonance techniques. Two phases can be distinguished: an almost isotropic ferromagnetic phase in insulating layers and an anisotropic ferromagnetic phase in the metallic Ga1− xMn xAs. Under a strong magnetic field the field-induced insulator-to-metal transition is accompanied by the change from the ferromagnetic to the ferrimagnetic phase. [ABSTRACT FROM AUTHOR] more...