The resistivity of the anisotropic semiconductor p-CdSb is investigated in a wide temperature range of T = 1.9-300 K in pulsed magnetic fields up to B = 25 T. Two not intentionally doped single-crystalline samples oriented along the crystallographic axes [100] (no. 1) and [010] (no. 2) are used for measurements of the resistivity, ρ, in transversal magnetic field configuration. Below T ≈ 8 K the resistivity follows the laws ln ρ ∼ C B 2 for B < B c and ln ρ ∼ S B 7/12 for B > B c , where the coefficients C and S do not depend on T , and B c ≈ 5-7.5 T. These are characteristics of nearest-neighbour hopping conductivity. The coefficients C and S depend on the direction of B, and their ratios agree completely with the values calculated with the components of the hole effective mass. The acceptor concentrations, N 1 ≈ 4.3 × 10 16 cm −3 and N 2 ≈ 7.6 × 10 16 cm −3 for no. 1 and no. 2, respectively, are relatively close to the critical value of the metal-insulator transition (MIT), N c ≈ 1.2×10 17 cm −3 . This leads to enhancement of the mean localization radii, a * 1 ≈ 78 Å in no. 1 and a * 2 ≈ 126 Å in no. 2, with respect to the value of a * 0 ≈ 50 Å far from the MIT determined by an asymptote of the wavefunction at a large distance from the impurity centre.

The Hall effect in the anisotropic II-V group semiconductor p-CdSb is investigated at temperatures between T = 3.6 and 200 K and pulsed magnetic fields up to B = 25 T in unintentionally doped samples oriented along the crystallographic axes [100] and [010]. The Hall coefficient, R(B, T ), with B [001] exhibits in low fields a flat region followed by a descending interval when B is increased. This behaviour is attributed to the presence of two groups of holes with concentrations p 2 (T ) > p 1 (T ) and mobilities µ 2 (T ) < µ 1 (T ), respectively. The analysis of p 1 (T ) and p 2 (T ) demonstrates that below T cr ∼ 20 K and down to ∼6-7 K the low-mobility carriers p 2 are itinerant holes in a deeper acceptor band A 2 with an energy E 2 ≈ 6 meV. The high-mobility carriers p 1 are at all temperatures T < T cr holes activated thermally from A 2 to itinerant states of a shallower acceptor band A 1 with an energy E 1 ≈ 3 meV. At T > T cr p 1 and p 2 are related to the holes activated to the light-and heavy-hole bands, respectively. The analysis of µ 1 (T ) and µ 2 (T ) confirms the existence of the heavy-hole band or a non-equivalent maximum and two equivalent maxima of the light-hole valence band.

The Hall effect in the II-V group semiconductor n-CdSb doped with In is investigated in pulsed magnetic fields up to B = 25 T and temperatures between T = 2 and 77 K for samples oriented along the [0 1 0] and [0 0 1] crystallographic axes. The Hall coefficient, R (B, T ), exhibits a sequence of an almost flat region followed by a descending interval and an upturn when B is increased. The decrease of R (B, T ) is interpreted by the presence of two groups of electrons with concentrations n 2 (T ) > n 1 (T ) and mobilities µ 2 (T ) < µ 1 (T ). Analysis of n 1 (T ) and n 2 (T ) demonstrates that the high-mobility carriers n 1 are the conduction band (CB) electrons, whereas the low-mobility carriers n 2 are itinerant electrons of a lower resonant impurity band (IB), having at low T energies of E i ∼ 3−4 meV above the CB edge. In addition, near the CB edge lies a higher IB containing only localized electron states. The IBs are split by spin to states differing by an energy E i ≈ 0.9 meV. The upturn of R (B, T ) in the high-field region is explained by the redistribution of the electrons between the IBs due to the decrease of E i when B is increased. The mobility of the CB electrons is determined presumably by strong anisotropic scattering on neutral impurity centres, accompanied at high T by isotropic scattering on acoustic phonons, whereas scattering from ionized impurities is small.

The resistivity of YBa2Cu3O7−δ (YBCO) films deposited by a pulsed laser from nanograined targets doped with various amounts of BaZrO3 (BZO) is investigated in the thermally activated flux-flow (TAFF) regime, where the activation energy, U, has a linear temperature dependence. It is found that the magnetic field dependence of the irreversibility temperature, Tirr(B), has a maximum at some optimal BZO concentration, which depends on the applied magnetic field. Our results show that the superconducting materials used in different magnetic fields need optimization of the dopant concentration to achieve the best properties for various applications.

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