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Electron paramagnetic resonance (EPR) of centers produced in porous silicon (PS) by heat treatment in air is investigated. The properties of these centers are compared with the defects present in as‐prepared PS or activated by treatment of the specimens with ethanol. The native defects of PS and those produced by thermal annealing show different saturation behavior of the EPR spectra when the microwave power is increased. Also, their spin‐dependent recombination processes are different. The dependence of the EPR line intensity on the thermal annealing time at temperatures of 150–500 °C obeys a law characteristic to a diffusion process with an activation energy of 0.9 eV. This value is close to the activation energy of oxidation of crystalline silicon surfaces with atomic oxygen.

Flow of magnetic flux, initiated by visible light, has been observed in a ceramic YBa 2 Cu 3 O x rf SQUID operated at 77 K in the nonhysteretic mode. The response of the SQUID to the applied optical power density is linear and has a coefficient of conversion ∼90 φ 0 /mW Oe, in units of the flux quantum φ 0 . Experiments made with illuminating a piece of the SQUID material inserted into its coupling hole show that the induced flux motion has exponential time dependence, especially at small time values. No influence of light on the 1/ f noise figure of the SQUID was observed.

Relaxation of the isothermoremanent magnetization has been investigated in ceramic Y-Ba-Cu-O samples with different grain sizes. It is found that the effective pinning energy U eff determined at different temperatures by using relaxation data of the remanent magnetic moment M IR and the relationship dln M IR / dln t =- kT / U eff has a maximum at a value of the magnetizing field H 0 corresponding to the most rapid increase of M IR with increasing H 0 . A phenomenological theory based on a critical- state model has been developed to describe these phenomena. The main conclusion of our analysis is that the dependence of U eff on H 0 can be attributed to the evolution of the distribution of the trapped flux (as H 0 is varied) without involving any assumptions about the dependence of the pinning barrier on the field.

Low-field, low-temperature static susceptibility measurements are reported for some CoAl1-xTx alloys with small concentrations of T = Cr, Fe, Co, Ni or Cu. All these alloys show field cooling effects. With increasing amount of T atoms spin-glass, mictomagnetic or ferromagnetic behaviour is observed. The Cr, Co and Cu alloys are in a spin-glass regime and pass subsequently through a cluster glass and reentrant regimes at the examined concentrations whereas the Fe and Ni alloys are mictomagnetic.

The influence of heterostructure quality on transport and optical properties of GaAs/AlGaAs single quantum wells with different qualities was studied. In a conventional sample-A, the transport scattering time and the quantum scattering time are small and close to each other. The interface roughness scattering is a dominant scattering mechanism. From comparison between theory and experiment, interface roughness with fluctuation height 2.5 Angstrom and the lateral size of 50-70 Angstrom were estimated. For samples introducing superlattices instead of AlGaAs layers or by utilizing growth interruption, both the transport and PL measurements showed that interfaces were rather smooth in the samples. The two scattering times are much longer. The interface roughness scattering is relegated to an unimportant position. Results demonstrated that it is important to control the formation of heterostructures in order to improve the interface quality.

YBCO nanopowder consisting of 1–3 nm thick and 40 nm wide particles has been used to make silver clad superconducting tapes. After annealing in nitrogen at 945 °C for 10 h a critical current of 5.02 A (3300 A/cm2) was attained. Annealing in mixed atmosphere of oxygen and nitrogen was also carried out and this procedure produced tapes with a critical current of 2.83 A (2200 A/cm2). These tapes show very good characteristics in magnetic fields.

AdetailedstudyofthemagneticandtransportpropertiesofSi1−xMnx (x ≈ 0.35)filmsispresented.Weobserve the anomalous Hall effect in these films up to room temperature. The results of the magnetic measurements and the anomalous Hall effect data are consistent and demonstrate the existence of long-range ferromagnetic order in the systems under investigation. A correlation of the anomalous Hall effect and the magnetic properties of the samples with their conductivity and substrate type is shown. A theoretical model based on the idea of a two-phase magnetic material, in which molecular clusters with localized magnetic moments are embedded in the matrix of a weak itinerant ferromagnet, is discussed and used to explain experimental results. The long-range ferromagnetic order at high temperatures is mainly due to the Stoner enhancement of the exchange coupling between clusters through thermal spin fluctuations (“paramagnons”) in the matrix. Theoretical predictions do not contradict experimental data when model parameters of a plausible order of magnitude are used.

The temperature dependence of the resistivity, ρ, of ceramic La(1 - x)Sr(x)Mn(1 - y)Fe(y)O(3) (LSMFO) samples with x = 0.3 and y = 0.03, 0.15, 0.20 and 0.25 (or simply #03, #15, #20 and #25, respectively) is investigated between temperatures T ∼ 5 and 310 K in magnetic fields B up to 8 T. Metallic conductivity in #03 is changed eventually to activated in #25. In #15 and #20 the behavior of ρ(T) is more complicated, comprising of two extremes, divided by an interval of metallic behavior in #15, and two inflections of ρ(T) in #20 within similar intervals ΔT below approximately 100 K. Mott variable-range hopping (VRH) conductivity is observed in #15 above the ferromagnetic Curie temperature, T(C). In #20 the Mott VRH conductivity takes place in three different temperature intervals at TT(C), T close to T(C) and TT(C). In #25, the Mott VRH conductivity is observed in two different intervals, above and below T(C), divided by an intermediate interval of the Shklovskii-Efros VRH conduction regime. Analysis of the VRH conductivity yielded the values of the localization radius, α, and the dependence of α and of the density of the localized states, g, near the Fermi level, on B. Above T(C) the localization radius in all samples at B = 0 has similar values, α approximately 1.0-1.2 Å, which is enhanced to α approximately 3.3 Å (#20) and 2.0 Å (#25) below T(C). The sensitivity of α and g to B depend on y and T. The complicated behavior of the mechanisms of the hopping charge transfer, as well as of the microscopic parameters α and g, is attributable to different electronic and magnetic phases of LSMFO varying with temperature and Fe doping.

A novel method for the synthesis of composite nanomaterials is suggested. Glassy carbon–metal (Au, Ag) composite materials are obtained in which the carbon matrix contains mesopores and metals are present in the form of nanoparticles distributed over the matrix. The sizes of nanoparticles are 10 and 23 nm for Au and Ag, respectively, while the specific surface area of the pores of materials ranges from 25 to 300 m2/g. A surprisingly high magnetic susceptibility of Au and Ag composites is revealed. © 2015, (publisher). All rights reserved.

The compositional variation of the elastic coefficients C11 and C33 for TlGa(S1−xS2 layer mixed crystal are discussed using Brillouin scattering measurements. Clear anomalies are observed for the longitudinal phonons propagating parallel to the (001) plane (elastic coefficient C11) at xc≅0.8 and xc≅0.3 in TlInxGa1−x S2 and TlGa(S1−xSex)2, respectively. These anomalies are explained by the formation of infinite clusters. A considerable difference in the rate of change of the elastic coefficient C33 with the composition for the mixed crystals TlGa(S1−xSex) 2 and TlInxGa1−xS2 is observed. The temperature variation of C33 for a TlIn0.95Ga0.05S2 mixed crystals is also given and the results are discussed.

We have investigated magnetic properties of porous silicon prepared by anodical etching of n- and p-type Si wafers. Measurements with a SQUID magnetometer have revealed in our samples ferromagnetism characterized by hysteretic behaviour, saturation in fields above 1.3 T and a remanent moment persisting up to Tc ⋍ 570 K. Electron paramagnetic resonance investigations have shown the presence of paramagnetic centers related with silicon dangling bonds.

Time-resolved photoluminescence (PL) spectra of porous Si have been investigated between 25 and 295 K. At high temperatures the PL band shows within a period of 110 μs after excitation a continuous redshift from 630 to 675 nm. In the ns-regime a rich fine structure of the PL band was observed. This could be decomposed into three peaks and their associated phonon replica with the 1100 cm-1 stretching mode of Si-O-Si. These peaks are located in the region of the predicted lowest exciton transitions of porous Si.

Photoinduced magnetic flux has been observed recently in normal metals exposed to unpolarized visible light. This effect is partly due to the fact that the light reflected from a metal surface transfers to the conduction electrons some of its quasimomentum. This creates a dc surface current which, for an appropriate geometry, brings about the photomagnetic effect. There is another contribution to the current that is due to anisotropy of the probabilities of electron transitions induced by the light, in combination with diffuse reflection of the electrons at the surface. Both contributions are compared. The relation between them may be particularly sensitive to the polarization of the light.

The electrical conductivity of (Zn1-xMnx)3As2 solid solutions with 0

Low field magnetic measurements have been made on AlCo alloys between 4.2–180 K. Using magnetic susceptibility and small angle X-ray scattering data simultaneous appearance of a spin glass phase and growth of clusters in the samples could be observed. With increasing amount of Co a phase with mixed spin glass and ferromagnetic properties could be found before transition to the ferromagnetic phase. Influence of thermal treatment on mictomagnetic behaviour of AlCo alloys is briefly discussed.

Persistent photoconductivity (PPC) and metastable photoinduced superconductivity, recently discovered in semiconducting ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6+\mathit{x}}$, have been investigated over the oxygen content of 0x1. Under exposure of semiconducting ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6+\mathit{x}}$ films (x\ensuremath{\simeq}0.4) to visible light their resistance is found to decrease drastically. After interrupting the irradiation the resistance persists at this reduced level provided that the temperature is kept below 270 K. When the illumination dose is increased the semiconductorlike behavior of the films progressively changes to that of a metal and a superconductor. Prolonged irradiation leads to complete loss of resistivity below 5 K and simultaneous growth of a diamagnetic moment in the films, revealing pronounced enhancement of their superconducting properties. A slow relaxation of the PPC state was found only by warming the sample near to room temperature where it could be described by a thermally activated process with an energy barrier of \ensuremath{\sim}1 eV. The observed phenomena are attributed to photoexcitation of extra mobile holes into ${\mathrm{CuO}}_{2}$ planes, allowing a metastable superconducting phase to be initiated. We also discuss feasible microscopic mechanisms of PPC in oxygen-deficient Y-Ba-Cu-O films. It is suggested that the photoinduced superconductivity may have applications in fabrication of in situ optically tunable weak-link devices.

Magnetic properties of the semimagnetic semiconductor (Zn 1-x Mn x ) 3 As 2 (for short, ZMA) with 0.001≤x≤0.13 have been investigated at temperatures between 4 and 300 K. It is shown that the magnetic susceptibilities of the samples cooled in zero external field (ZFC) and in a field (FC) are different for compositions with x≥0.02. At Mn concentrations 0.08≤x≤0.13 freezing of the moments is observed around T f ∼200 K

Temperature dependence of the thermoremanent magnetization (MR(T)) has been investigated in YBa2Cu3O7-δ powders and ceramics after cooling the sample in a magnetic field. When the density of vortices in the grains in high, MR(T) can be expressed with an exponential law by using an effective activation energy Ueff related to interactions between vortices. In powders, the value of Ueff does not depend on the size of particles. Measurements with ceramics give different values of Ueff for samples prepared by using different heat treatment times. Finally, the temperature dependence of MR(T) is discussed within the framework of a vortex glass model. This approach is supported by a memory effect observed in MR(T).

Isothermoremanent magnetization and its relaxation with time have been investigated in ceramics and powders of YBa 2 Cu 3 O 7−δ at different temperatures after magnetizing the sample in a field of H ext eff ≈0.7 eV, independent of H ext . In the ceramic material U eff was found to depend strongly on the applied field reaching a value of 5 eV at 10 Oe and decreasing steeply when the magnetizing field was increased. The field dependence is discussed by using a model which takes into account the interaction between vortices.

It is shown that below T f ≈ 200 K the d.c. susceptibility of the semimagnetic semiconductor (Cd 1- x Mn x ) 3 As 2 cooled in zero magnetic field differs from that observed after cooling the sample in a field. This phenomenon was found only in the range of H ≤ 300 Oe. We attribute it to freezing of magnetic clusters according to local anisotropy fields in the sample. The high value of the freezing temperature indicates relatively strong intracluster magnetic interactions.

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 refected 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.

Magnetostatic interaction between the tip of a magnetic force microscope (MFM) and an Abrikosov vortex line is theoretically analysed in isotropic superconductors and in high-Tc materials with the magnetic field oriented along the c axis. The predicted forces are of the order of 10-9-10-10 N suggesting that it is possible to observe the distribution of the magnetic field of a single vortex by existing MFM techniques. The influence of the surrounding vortex lattice on measurements is also discussed.

Metallic vanadium samples were oxidized in air by a cw Nd:YAG laser. The structure of developed V 2 O 5 crystals was investigated by optical and scanning tunneling microscopy (STM). Ripple morphologies with submicron spatial period have been observed. The grating-like structures have been attributed to the interference of surface scattered electromagnetic waves with incident laser light. The dispersion of the surface capillary waves has been taken into account since the oxide has developed partly in a liquid phase.

Transport properties and photoluminescence (PL) spectra have been studied in three types of GaAs AlGaAs single quantum wells with very different quality. For sample-A, with rough interfaces, both the transport scattering time and the quantum scattering time extracted from transport measurements are rather short and close to each other. The interface roughness (IFR) is found to be characterized by a step height Δ of 3 A and a lateral length Λ of 50 A. Meanwhile, the wider line-width and lower luminescence efficiency shown in the PL spectra of sample-A are in one-to-one correspondence with the larger scattering rate and the rougher heterostructures containing more non-radiative centers near the interfaces. Our work also shows that reduction of the interface roughness can be achieved by either replacing AlGaAs layers by (GaAs) 4 (AlAs) 2 superlattices (sample-B) or employing growth interruption at the heterointerfaces (sample-C).

The resistivity components ϱab and ϱc of a large (2 × 2 × 1 mm3) YBa2Cu3O7-x single crystal have been measured. The results reveal a step-wise transition into the superconducting state indicating a multiple-single-crystal structure of the sample. Surface topologies of the a-b and the c planes of the crystal were investigated by a scanning tunneling microscope confirming the existence of the layered (plate-like) structure perpendicular to the c-axis. The average thickness of one layer was found to be ≈ 0.5 μm.

Dispersion of the acoustic anomalies for hypersonic phonons studied by Brillouin scattering has been found in region of a typical diffuse ferroelectric phase transition in PbMg1/3Nb2/303 Both the velocity dip and the damping maximum centred on the mean Curie temperature are connected with fluctuation contributions. The value of anomalies is decreased by dispersion at high frequencies. The relaxation contribution dispersion leads to the appearing of an ordinary shifted maximum of damping and the stretching of velocity step when measuring at Brillouin frequencies.

Surface and subsurface structures of porous GaN prepared by anodizing epitaxial GaN layers grown on SiC substrates are investigated by atomic-force microscopy. Comparison of the images of the porous GaN surfaces with those taken on planes cleft perpendicular to the surface shows that the pores are formed along the boundaries of columnar structures of the original GaN films. X-ray investigations show that the porous GaN has less residual stresses than the initial GaN epitaxial layers. Use of porous GaN as a buffer layer for growth of low-stress GaN is proposed.

Magnetoelectrical measurements were performed on diodes and bulk heterojunction solar cell blends (BHSCs) to clarify the role of formation of Coulombically bound electron-hole (e-h) pairs on the magnetoresistance (MR) response in organic thin-film devices. BHSCs are suitable model systems because they effectively quench excitons but the probability of forming e-h pairs in them can be tuned over orders of magnitude by the choice of material and solvent in the blend. We have systematically varied the e-h recombination coefficients, which are directly proportional to the probability for the charge carriers to meet in space, and found that a reduced probability of electrons and holes meeting in space lead to the disappearance of the MR. Our results clearly show that MR is a direct consequence of the e-h pair formation. We also found that the MR line shape follows a power-law dependence of ${B}^{0.5}$ at higher fields.

Magnetoresistance (MR) of oriented single crystals of the anisotropic semiconductor p-CdSb doped with 2 at% of Ni is investigated between T =1.5 and 300 K in transversal pulsed magnetic fields up to B =30 T. In fields B ∼4–15 T at T below 4.2 K, the resistivity obeys the law ln ρ ∼ η [ Bϕ ( B )] 1/2 with ϕ ( B )= a (0)/ a ( B ), where a is the carrier localization radius and parameter η depends on a (0), on the acceptor concentration N A and on the direction of the magnetic field with respect to the crystallographic axes, but does not depend on T . Such behavior gives evidence for MR realized by hopping charge transfer over the nearest-neighbor sites in strong magnetic field. The analysis of the experimental data yields the values of η , agreeing with calculated ones within an error of 10%, taking into account the effects of the anisotropy of the acceptor states and of the explicit dependence of a ( B ) due to the increase in the activation energy of shallow acceptors in magnetic field and the sensitivity of the metal–insulator transition to B .

We report on magnetotransport studies of regio regular poly (3-hexyl thiophene) (RRP3HT) based diodes and P3HT: 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]- methanofullerene (PCBM) bulk heterojunction solar cells. While the P3HT diodes with non-magnetic electrodes ITO and Al show up to 16% positive magnetoresistance (MR) under 300 mT magnetic field at room temperature, solar cells with much reduced electronhole pair (e-h) formation probability show almost negligible MR clearly suggesting that MR in organic semiconductors is strongly dependent on the probability of forming Coulombically bound e-h pairs. Voltage and temperature dependence of MR sign and magnitude is discussed for the diode devices which provides important insight of the scientifically puzzling yet technologically very promising magnetotransport properties of organic semiconductor based devices.

Photoinduced superconductivity has been investigated in YBa 2 Cu 3 O 6.4 films near to the semiconductor-metal transition. Light-induced changes in the resistance and growth of the diamagnetic moment were observed. The data revealed a dependence between the photoinduced reduction of the normal state resistance and the increase of the onset temperature of superconductivity in the films. Prolonged irradiation led to a seemingly complete loss of resistivity below 5 K. These phenomena are attributed to photogeneration of additional mobile holes in CuO 2 layers resulting in superconductivity.

Superconducting thick films with the nominal composition of Bi1.9Pb0.4Sr1.9Ca2.1Cu3.2O10 were prepared by the screen-printing method, using an oxalate synthesis for making the paste, and different heat treatments for final samples. A large difference in the structural and superconducting properties between the unmelted and melted samples, and small deviations between the melted and variously annealed specimens were observed. In the first case, the structure is determined by randomly distributed small microcrystals, while in the second, by highly orientated big ones, which results in dissimilar electrical and magnetic features. Therefore the magnetic moment and superconducting material ratio are bigger in the unmelted samples, but in the melted ones, the superconductivity can be characterized by much higher electrical and magnetic parameters. In particular, the transport critical current has conspicuously greater values in the melted as compared to the unmelted samples. In some melted specimens a hyperdiamagnetic signal has been found up to 242 K, induced by the fine details of the preparation technique. The simplest possible reason for this is the diamagnetic Cu−O content in the samples.

Using different batches of starting materials (samples I, TINO 3 , CaO, Ba 2 Cu 3 O 5 ; II, TINO 3 , CaO, BaO, CuO; III, TINO 3 , CaO, Ba(NO 3 ) 2 , CuO; IV, TINO 3 , CaO, BaCuO 2 ; V, TINO 3 , CaO, Ba(NO 3 ) 2 , CuO, O 2 ) and the same heat treatment process, high T c superconducting systems of nominal composition TICaBaCuO 4.5 were prepared. Different superconducting phases were formed depending on the starting compounds used. Specimens I and IV had a single-phase (2,1,2,2) character. In samples II and III the dominant (2,1,2,2) phase was accompanied by (2,0,2,1) and by (1,2,2,3) and (2,2,2,3) phases in small quantity, respectively, while specimens V can be characterized by the existence of CuO and Cu 2 O beside the chief (2,1,2,2) phase. The superconducting properties were affected by starting materials, which manifests itself in the difference in onset and critical temperatures, lower and upper critical magnetic fields, paramagnetic limits, coherence length, penetration depth and Ginzburg - Landau parameter of specimens of different kinds. Due to the weak coupling created by interstitial material, different intergrain, intragrain and direct transport critical currents were determined, depending on the type of samples. The main aim of this work was to compare the experimental data with the corresponding theories to draw conclusions on the role of the starting compounds.

Electron paramagnetic resonance (EPR) spectra of radiation defects induced by low-energy protons (100 keV) in a thin near-surface layer (L

The phenomenon of persistent photoconductivity in YBa2Cu3O6+x (x ≈ 0.4) films near the semiconductor-metal transition has been studied. Transport and magnetic measurements of the illuminated films were performed. The transition to the metallic state and photoinduced superconductivity have been observed. The mechanism of persistent photoconductivity in reduced YBa2Cu3O6+x films is also discussed.

It has been shown, that different starting materials result in Tl−Ca−Ba−Cu−O superconductors of different type even at the same heat treatment process. This manifests itself in the developing structure, in the number, share-rate and superconducting properties of the occurring phases as well. Microcrystals, phase-compositions, crystallinities, unit cells, onset and critical temperatures, magnetic flux exclusions, critical currents, magnetizations and critical magnetic fields essentially unlike from each other have been observed, depending on the starting materials. The presence of a starting compound having low melting point, as Ba(NO3)2 can cause a more compact, better superconducting final product, implying better connection between the grains.

Low-field magnetization has been investigated in powders of YBa 2 Cu 3 O 7- δ using samples with different maximal characteristic particle sizes d max of between 2.4 and 7.4 μm. Measurements of the thermoremanent magnetization reveal the existence of a threshold field H th corresponding to trapping of a single flux quantum Φ 0 in microcrystal: H th =(1.1±0.2) Φ 0 / d 2 max . Flux creep was found to depend on the grain size, giving evidence for the presence of a surface barrier of flux trapping. A reversible temperature dependence of the thermoremanent magnetization has been observed. This effect is attributed to a local field created by particles containing trapped flux.

The structural, electrical and magnetic properties of screen-printed superconducting BiPbSrCaCuO thick films have been investigated. The films were either solid state sintered or first melt processed and then annealed over a long period of time. The films were primarily made up of the 2223 phase. The solid state sintered films had randomly arranged flaky crystals. The melt processed films were strongly textured with the (001) planes of the large plate-like grains parallel with the film surface. A pulse method was utilized for critical current measurements, which had the advantage of excluding the effect of local heating of the samples while at the same time increasing the sensitivity of measurement. The magnetic properties of both the solid state sintered and melt processed films were similar, but the transport critical parameters of the melt processed films were superior; the best films having their T c at 105 K and a critical current density of ≈ 2000 A cm −2 at 77 K in a zero external magnetic field. Variation of annealing procedures resulted in clearly different microstructures, which in turn manifested itself in differing superconducting properties. From the point of view of applications, the melt texturing process seems to be promising.

Optically induced changes have been observed in the magnetic properties of the ceramic superconductor ${\mathrm{La}}_{1.8}$${\mathrm{Ba}}_{0.2}$${\mathrm{CuO}}_{4}$. The most prominent feature of our data is the light-induced change of the magnetic moment, proportional to ${\mathit{T}}^{\mathrm{\ensuremath{-}}1/2}$exp(a/kT), where a is a constant when the sample is cooled below \ensuremath{\sim}${\mathit{T}}_{\mathit{c}}$/2. Results obtained in applied magnetic fields of 1, 9, and 26 Oe suggest that the observed effect has contributions from a weakening of the intergranular Josephson junctions under illumination as well as from an additional form of optically induced flux creep, which depends on the applied magnetic field.

Tl−Ca−Ba−Cu−O compounds of the nominal composition of (1, 1, 1, 1) have been prepared from different starting materials and with the same heat treatment process. During the investigation of their properties a diamagnetic signal has been found up to the temperature of 132 K. This hints at the existence of a certain material content distributed into discrete superconducting domains. The parameters of it reflect a superstructure of the (2, 2, 2, 3) and (2, 1, 2, 2) compositions having a time-dependent behaviour. On the basis of the signal levels at 132 K and 4.2 K, the quantity of the high temperature superconducting material is about 0.01% of the total one at liquid He temperatures.

The problem of transformation of the quasiclassical Eilenberger theory to the one-parameter London model is considered for the mixed state of clean type-II superconductors. Numerical computations demonstrate that introduction of a field dependent coherence length ${\ensuremath{\xi}}_{h}(B)$ is enough for description of the magnetic field distribution in the vortex core of a superconductor. It is found that the shape of ${\ensuremath{\xi}}_{h}(B)$ has strong temperature dependence. The comparison between $s$- and $d$-wave pairing symmetry is done. Different behavior of ${\ensuremath{\xi}}_{h}(B)$ in triangular and square vortex lattices is found.

We report results of investigations of structural and transport properties of GaAs/Ga(1-x)In(x)As/GaAs quantum wells (QWs) having a 0.5-1.8 ML thick Mn layer, separated from the QW by a 3 nm thick spacer. The structure has hole mobility of about 2000 cm2/(V*s) being by several orders of magnitude higher than in known ferromagnetic two-dimensional structures. The analysis of the electro-physical properties of these systems is based on detailed study of their structure by means of high-resolution X-ray diffractometry and glancing-incidence reflection, which allow us to restore the depth profiles of structural characteristics of the QWs and thin Mn containing layers. These investigations show absence of Mn atoms inside the QWs. The quality of the structures was also characterized by photoluminescence spectra from the QWs. Transport properties reveal features inherent to ferromagnetic systems: a specific maximum in the temperature dependence of the resistance and the anomalous Hall effect (AHE) observed in samples with both "metallic" and activated types of conductivity up to ~100 K. AHE is most pronounced in the temperature range where the resistance maximum is observed, and decreases with decreasing temperature. The results are discussed in terms of interaction of 2D-holes and magnetic Mn ions in presence of large-scale potential fluctuations related to random distribution of Mn atoms. The AHE values are compared with calculations taking into account its "intrinsic" mechanism in ferromagnetic systems., 15 pages, 9 figures

ZnSe:Cr-based infrared (IR) laser operating at room temperature is of great interest shows the near-edge photoluminescence (PL) spectra of Cr-doped ZnSe observed under 337.1 nm excitation. A broad blue PL band at 427 nm is observed for lightly Cr-doped samples and the sample doped with Cr from the Bi + Cr melt. Blue PL band is excited by two-step complementary photoionization transitions of chromium ions. Free carriers photo-generated in the conduction and valence bands of ZnSe participate in the band-to-band transitions responsible for the blue emission. Free holes generated in the valence band under chromium ionization are efficiently trapped by shallow acceptor centres being active in the blue emission process. The second photon, which is absorbed by photo-generated Cr+ state, induces a complementary ionization transition to the conduction band. Thus, both types of free carriers are photo-generated and responsible for the blue PL.

We extend the Ginsburg-Landau solution for cutoff function in London equation to low temperatures by solving numerically the quasiclassical Eilenberger equations in mixed state of $s$-wave superconductors. As a result the nonlocal generalized London equation (NGLE) is obtained. The magnetic field and temperature dependence of the cutoff function parameter ${k}_{1}(B,T)$ are calculated. Due to Kramer-Pesch effect ${k}_{1}$ decreases strongly at low temperatures. It is also found that ${k}_{1}$ has a minimum at a value of magnetic field depending on temperature. We reduce the NGLE model to an effective local model and calculate the value of an effective penetration depth ${\ensuremath{\lambda}}_{\mathrm{eff}}(B,T)$. The sublinear field dependence of ${\ensuremath{\lambda}}_{\mathrm{eff}}$ is predicted that agrees with experimental $\ensuremath{\mu}$SR results for the penetration depth of magnetic field in the $s$-wave superconductor ${\mathrm{V}}_{3}\mathrm{Si}$ and ${\mathrm{NbSe}}_{2}$.

We describe a substrate heater constructed for use in an oxidizing environment in the temperature range of T⩽900 °C. The heating element is an ordinary projection lamp working in ambient near the end of a quartz tube fixed with a flange to a vacuum chamber. On the vacuum (outer) side of the tube is a smooth fitting stainless steel cylinder that conducts the heat to the region of the substrate. For fixing or removing the substrate the cylinder can be simply pulled off its position on the quartz tube. The heater that is described has been used, for example, for laser ablation of YBa2Cu3O6+x superconducting films.