Co3O4, ZnFe2O4, CoFe2O4, ZnCo2O4, and Fe3O4 thin films were fabricated by pulsed laser deposition at high and low temperatures resulting in crystalline single‐phase normal, inverse, as well as disordered spinel oxide thin films with smooth surface morphology. The dielectric function, determined by spectroscopic ellipsometry in a wide spectral range from 0.5 to 8.5 eV, is compared with the magneto‐optical response of the dielectric tensor, investigated by magneto‐optical Kerr effect spectroscopy in the spectral range from 1.7 to 5.5 eV with an applied magnetic field of 1.7 T. Crystal field, inter‐valence, and inter‐sublattice charge transfer transitions, and transitions from O2p to metal cation 3d or 4s bands are identified in both the principal diagonal elements and the magneto‐optically active off‐diagonal elements of the dielectric tensor. Depending on the degree of cation disorder, resulting in local symmetry distortion, the magneto‐optical response is found to be strongest for high crystal quality inverse spinels and for disordered normal spinel structure, contrary to the first principle studies of CoFe2O4 and ZnFe2O4. The results presented provide a basis for deeper understanding of light–matter interaction in this material system that is of vital importance for device‐related phenomena and engineering.

Soil phytoextraction is based on the ability of plants to extract contaminants from the soil. For less bioavailable metals, such as Pb, a chelator is added to the soil to mobilize the metal. The effect can be significant and in certain species, heavy metal accumulation can rapidly increase 10-fold. Accumulation of high levels of toxic metals may result in irreversible damage to the plant. Monitoring and controlling the phytotoxicity caused by EDTA-induced metal accumulation is crucial to optimize the remedial process, i.e. to achieve maximum uptake. We describe an EDTA-application procedure that minimizes phytotoxicity by increasing plant tolerance and allows phytoextraction of elevated levels of Pb and Cd. Brassica juncea is tested in soil with typical Pb and Cd concentrations of 500 mg kg-1 and 15 mg kg-1, respectively. Instead of a single dose treatment, the chelator is applied in multiple doses, that is, in several small increments, thus providing time for plants to initiate their adaptation mechanisms and raise their damage threshold. In situ monitoring of plant stress conditions by chlorophyll fluorescence recording allows for the identification of the saturating heavy metal accumulation process and of simultaneous plant deterioration.

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In this paper a compact, portable instrument is presented for the measurement of full chlorophyll fluorescence kinetics of plants at two different wavelengths. The instrument uses a 635 nm laser diode as a light source with variable gain driving that allows excitations at selectable actinic levels. The plant fluorescence is detected, at 690 nm and 735 nm, through a specially mixed three-branch optical fibre bundle. Large scale field monitoring of vegetation is made possible by the utilization of PC/104-form embedded electronics including a low power, IBM PC/386-compatible single board computer (SBC) with non-volatile flash memory. Application of a general purpose SBC and task oriented programming offers in situ data evaluation making process control possible. The capabilities of the instrument were demonstrated in monitoring soil phytoremediation processes.

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