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The structural and transport properties of GaAs/Mn/GaAs/InxGa1−xAs/GaAs quantum wells (x≈0.2) with Mn δ-layer (4–10 at. %), separated from the well by a GaAs spacer, have been studied. The hole mobility in the investigated structures has exceeded the values known for magnetic III-V heterostructures by two orders of magnitude. For structures with the conductivity of the metal type, we have succeeded to observe at low temperatures Shubnikov–de Haas oscillations just confirming the two dimensionality (2D) of the hole energy spectrum. Exactly those 2D holes promote the ferromagnetic ordering of the Mn layer. That has been proven by (i) observing maxima (at 25–40 K) in temperature dependencies of the resistance, which positions agree with calculated values of Curie temperatures (for structures with the indirect interaction of Mn atoms via 2D holes), and (ii) revealing the negative spin-dependent magnetoresistance (NMR) as well as the anomalous Hall effect (AHE), which values are also in good agreement with calculations relating to ferromagnetic 2D III-V systems. As for the structures with the insulator type of the conductivity, their NMR and AHE features evidence the phase separation—the sample fragmentation with the formation of mesoscopic ferromagnetic areas separated by paramagnetic strata of the high tunnel conductivity.

Mechanisms of the resistivity, ρ, of single crystal samples oriented along the [100] (No 1), [010] (No 2) and [001] (No 3) axes of anisotropic semiconductor p-CdSb doped with 2 at.% of Ni are investigated. In zero magnetic field the Mott type variable-range hopping (VRH) conductivity is observed in No 2 and the Shklovskii–Efros type in No 1 and No 3 at T≤2.5 K. The magnetoresistance (MR) of the samples obeys the law lnρ∼B2 up to B∼6 T. However, the temperature dependence of MR gives evidence for the Mott-VRH conductivity in No 1 at T≤4.2 K and the nearest-neighbor hopping conductivity in No 2 between T = 3 and 4.2 K and in No 3 between 1.5 and 4.2 K. From the experimental data the values of the localization radius and dielectric permittivity and details of their critical behavior near the metal–insulator transition, as well as the widths and the values of the density of the localized states, the acceptor energies, their concentrations and the anisotropy coefficients, are obtained.

A photoinduced magnetic moment has been observed in Cu and Al samples exposed to unpolarized visible light at low temperatures. It is shown that the light reflected from a metal surface transfers some of its quasimomentum to conduction electrons. This mechanism creates surface currents which, for an appropriate geometry, bring about the photomagnetic effect.

The magnetic properties of oriented CdSb single crystals doped with 2 at% of Ni are investigated. From measurements of magnetic irreversibility defined by deviation of the zero-field-cooled (ZFC) susceptibility from the field-cooled (FC) susceptibility, the value of the mean anisotropy field B K ∼ 4 kG is obtained. The ZFC susceptibility displays a broad maximum at a blocking temperature, T b , depending on B according to the law [T b (B)/T b (0)] 1/2 = 1 − B/B K with T b (0) ∼ 100 K. The field dependence of the magnetization exhibits saturation above ∼20-30 kG with values of M s different for B along the [1 0 0], [0 1 0] and [0 0 1] axes. The temperature dependence of M s is weak, increasing slightly upon cooling the sample below ∼100 K. The temperature dependence of the coercive field, B c (T), is weak above T b but is enhanced strongly with decreasing temperature below T b. The anisotropy of B c is inverted with respect to the anisotropy of M s. Such behaviour can be attributed to spheroidal Ni-rich Ni 1−x Sb x nanoparticles with a high aspect ratio, broad size distribution and distribution of the orientation of the major axis around a preferred direction. The relation B c B K and the anisotropies of M s and B c are consistent with reversal of the magnetization by the curling mode, whereas the T b (B) dependence is typical of the coherent rotation mode. This difference is connected to the proximity of the average transversal cluster radius to a critical value for transition between the two magnetization reversal modes within a wide crossover interval, due to broad distribution of the cluster sizes.