Zinc-blende CrAs/GaAs multilayers were grown by molecular beam epitaxy. It was certified that each CrAs layer maintains an epitaxial relationship with the zinc-blende GaAs structure judging from the reflection high-energy electron diffraction observation. The film contains thicker zinc- blende CrAs layers in total than the CrAs thin film directly grown on the GaAs substrate which has the critical thickness of 3 nm. It was clarified that the optimum thicknesses of CrAs and GaAs to keep a good epitaxial relationship are 2 ML and 2 ML, respectively. The electronic structure of the multilayer is thought to be close to that of the (Ga, Cr)As thin film which has 50% of Cr content judging from x-ray absorption spectroscopy measurements.

Polycrystalline europium monoxide (EuO) films doped with and without Gd were prepared using a reactive deposition method in a MBE system. Two different electron doping methods, Gd substitution and oxygen deficiency, enhance the Curie temperature (TC) and the temperature dependence of magnetization differently. Gd doping increases TC up to 125 K, while oxygen deficient samples enhance it above 150 K. The enhanced TC is attributed to the increase in the indirect exchange interaction between Eu2+ spins via conduction electrons. The resistivities as a function of temperature for both quasi-stoichiometric (QS) EuO and QS-GdxEu1−xO show maxima near 70 and 110 K, respectively. The conduction band magnetic splitting explains the resistivity behaviours. Both the temperature dependences of the large magneto-resistance and the absorption edge are also interpreted by the conduction band magnetic splitting mechanism. The unusual blue shift observed in Gd-doped samples is not yet understood.

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We have investigated the electronic structure of Zn1−xMxO (M: 3d transition metal) by x-ray absorption spectroscopy. Using configuration–interaction cluster-model analyses, electronic structure parameters have been deduced and their chemical trend is discussed. Results show that the p–d exchange constant Nβ is negative and large in cases of Mn, Fe, and Co, which is consistent with the enhancement of magnetic circular dichroism.

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