[en] This paper reviews recent milikelvin studies of magnetoconductance and noise in nanostructures of a diluted magnetic semiconductors n-Cd_1-xMn_xTe. These studies were particularly rewarding for probing the influence of magnetic ions upon mesoscopic phenomena. The accumulated results demonstrated the existence of a new driving mechanism of the universal conductance fluctuations in magnetic systems. Several signatures of spin-glass freezing were observed, such as the appearance of 1/f conductance noise, aging, thermal, and magnetic irreversibilities as well as strong increase in the amplitude of both conductance fluctuations and noise when temperature and the magnetic field were lowered below the freezing line. A statistical analysis of conductance noise made it possible to investigate the nature of excitations in spin-glass phase, and discriminate between competing theoretical models. (author)

No abstract available

[en] We present millikelvin studies of magneto-resistance for epitaxial films and wires of CdTe:In. In comparison to the data with theoretical predictions for the weakly localized regime we put into the evidence the presence of the temperature-induced dimensional crossovers in the studied systems. Our measurements probe the electron phase-breaking rate and indicate that the main dephasing mechanism arises from the electron scattering from thermal fluctuations of three- or two-dimensional electron liquid. (author)

[en] We report on iodine doping of molecular beam epitaxy (MBE)-grown Cd(Mn)Te quasi-bulk films and modulation-doped CdTe/Cd_1-yMg_yTe two-dimensional (2D) single quantum well structures. Modulation doping with iodine of CdTe/Cd_1-yMg_yTe structures resulted in fabrication of a 2D electron gas with mobility exceeding 10⁵ cm²/(Vs). This is the highest mobility reported in wide-gap II-VI materials

No abstract available

[en] We present a broad study by multiple techniques of the critical current and critical current density of a small but representative set of nominally identical commercial RE123 (REBa_2Cu_3O_7_−_δ, RE = rare Earth, here Y and Gd) coated conductors (CC) recently fabricated by SuperPower Inc. to the same nominal high pinning specification with BaZrO_3 and RE_2O_3 nanoprecipitate pinning centers. With high-field low-temperature applications to magnet technology in mind, we address the nature of their tape-to-tape variations and length-wise I _c inhomogeneities by measurements on a scale of about 2 cm rather than the 5 m scale normally supplied by the vendor and address the question of whether these variations have their origin in cross-sectional or in vortex pinning variations. Our principal method has been a continuous measurement transport critical current tool (YateStar) that applies about 0.5 T perpendicular and parallel to the tape at 77 K, thus allowing variations of c-axis and ab-plane properties to be clearly distinguished in the temperature and field regime where strong pinning defects are obvious. We also find such in-field measurements at 77 K to be more valuable in predicting 4.2 K, high-field properties than self-field, 77 K properties because the pinning centers controlling 77 K performance play a decisive role in introducing point defects that also add strongly to J _c at 4.2 K. We find that the dominant source of I _c variation is due to pinning center fluctuations that control J _c, rather than to production defects that locally reduce the active cross-section. Given the 5–10 nm scale of these pinning centers, it appears that the route to greater I _c homogeneity is through more stringent control of the REBCO growth conditions in these Zr-doped coated conductors. (paper)

No abstract available

[en] We have investigated magneto-photoluminescence spectra in a modulation n-doped CdTe/Cd_0.865Mg_0.135Te single quantum well in magnetic fields up to 40 T at low temperatures. High-mobility two-dimensional carriers (μ ∼ 130 000cm²/V s at n = 4.4 x 10¹¹cm^-2) realized in this new system exhibited photoluminescence anomalies associated with the integer and fractional quantum Hall effect. In addition to the oscillatory features of the peak shifts, we observed additional high-energy peaks at the Landau filling factor υ ≤ 2. Photoluminescence polarization was investigated in the region of various low Landau-fillings

[en] The high pressure Bridgman technique was used to growth Zn_1-xMn_xTe:P crystals. Under N₂ pressure of 30 atm., we obtained the p⁺-Zn_1-xMn_xTe single crystals 8-10 mm in diameter, with free-carrier densities as high as p ∼ 8 x 10¹⁸ cm^-3 and the room temperature conductivity ρ(RT) ∼ 30 a^-1 cm^-1. Magnetoresistance measurements were carried out down to 1.3 K and up to 6 T. In Zn_1-xMn_xTe:P a strong increase in the acceptor binding energy as well as immense (ρ(0,1.3 K)/ρ(6 T,1.3 K) > 10³) negative magnetoresistance are observed, by contrast, not seen in diamagnetic ZnTe:P. It is shown that these effects come from the formation of bound magnetic polarons and their destruction by an external magnetic field. (author)

No abstract available