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Spin splitting of conduction band electrons in In0.53Ga0.47As/In0.77Ga0.23As/InP heterostructures due to spin-orbit coupling is studied by performing Shubnikov–de Haas measurements on nongated and gated Hall bars. From an analysis of the beating pattern in the Shubnikov–de Haas oscillations, the spin-orbit coupling constant is determined. For a symmetric sample no beating pattern and thus no spin splitting is observed. This demonstrates that the k3 contribution to the spin-orbit coupling constant can be neglected. By applying an envelope function theory it is shown that the major contribution to the Rashba spin-orbit coupling originates from the band offset at the interface of the quantum well. Using gated Hall bar structures it is possible to alter the spin-orbit coupling by application of an appropriate gate voltage. A more negative gate voltage leads to a more pronounced asymmetry of the quantum well, which gives rise to a stronger spin-orbit coupling.

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Dielectric measurements of moist soils are used to determine water saturations. The degree of saturation of water is determined using a mixing law for the composite structure (soil, water, and air) which is verified experimentally. For the lower water saturation range (<60%), a particularly simple form for the relationship between fractional water content θ and measured dielectric constant can be formulated. In particular, for sandy soils at 23°C, the fractional water content is given by θ = 0.128(ϵc)½ − 0.204.

A low-Tc SQUID system was developed for measuring magnetic relaxation of polymer-coated magnetic nanoparticles (MNPs) in a liquid carrier (e.g. water). The system consists of two low-Tc SQUIDs which are electronically combined to form an axial gradiometer using high-bandwidth directly coupled FLL electronics. The system is operated in a magnetically shielded room. The magnetic relaxation of the investigated MNPs in a liquid carrier is dominated by Brownian motion. In a solid phase, when the MNPs are immobilized, the magnetization of the sample decays via the Néel mechanism. A similar situation occurs when the mobility of the MNPs is reduced by a biochemical binding reaction. This effect is used for identifying biological reactions for purposes of medical diagnostics, e.g. immunoassays. By investigating the magnetic relaxation of dried samples, quantities as small as 1 nmol Fe of -Fe2O3 were detected. In the first agglomeration assay the binding reaction of the biochemical model biotin-avidin complexes can be clearly identified down to concentrations of <1 µg avidin in a volume of 150 µl of human blood.