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Magnetic nanocomposites (MNC), in which nanoparticles of ferromagnetic metals are distributed in wide-gap dielectric matrices (Al2O3 or SiO2), are prospective materials for electronics due to their amenability to technological control of the concentration and size of ferromagnetic nanoparticles. Co/Al2O3 and Co/SiO2 MNC layers with Co concentrations below the percolation threshold were deposited on polycor substrates using electron-beam deposition in a vacuum (EB-PVD). Scanning electron microscopy showed the presence of tightly packed Co grains of irregular shape with sizes of 5–50 nm in MNC. Low-temperature measurements of the magnetization for MNC Co/Al2O3 were made in the temperature range 4–300 K and magnetic fields up to 10 kOe. The ‘magnetic exchange bias’ has been detected, and it increases with a rise in Co concentration. By studying the electrical properties of the MNC Co/Al2O3 and Co/SiO2 in the temperature range of 77–280 K, the Mott type electron transport hopping mechanism was established. We first observed the effect of a giant positive thermoelectric power in a magnetic field in MNC Co/Al2O3 and the effect of a negative magnetothermoelectric power in a Co/SiO2.Magnetic nanocomposites (MNC), in which nanoparticles of ferromagnetic metals are distributed in wide-gap dielectric matrices (Al2O3 or SiO2), are prospective materials for electronics due to their amenability to technological control of the concentration and size of ferromagnetic nanoparticles. Co/Al2O3 and Co/SiO2 MNC layers with Co concentrations below the percolation threshold were deposited on polycor substrates using electron-beam deposition in a vacuum (EB-PVD). Scanning electron microscopy showed the presence of tightly packed Co grains of irregular shape with sizes of 5–50 nm in MNC. Low-temperature measurements of the magnetization for MNC Co/Al2O3 were made in the temperature range 4–300 K and magnetic fields up to 10 kOe. The ‘magnetic exchange bias’ has been detected, and it increases with a rise in Co concentration. By studying the electrical properties of the MNC Co/Al2O3 and Co/SiO2 in the temperature range of 77–280 K, the Mott type electron transport hopping mechanism was established. We...

The current study describes the main morphological and the photocatalytic performance differences between three zinc oxide samples; commercially available, synthetized tetrapods, and synthetized oxygen-defected sample. Oxygen-defected ZnO particles were prepared through a novel one-step thermal heating of metallic zinc powder at 1000 °C in a small concentration of oxygen gas. On the other hand, the tetrapods ZnO sample was prepared under the same conditions but in a high concentration of oxygen gas. The three materials were characterized by XRD, Raman spectroscopy, SEM, EDX, DRspectroscopy and finally EPR. The oxygen-defected sample has a grey colour and it tends to have a distorted tetrapods structure with a multitude of defect surface VO-Zn2-x sites. Moreover, the absorption spectrum of the oxygen-defected sample showed a red-shift towards a visible light region as compared to that of commercial sample, with a calculated bandgap of 3.07 eV. The photocatalytic performance of the three materials was evaluated in the liquid phase decolourization of methyl green under the illumination of black UV light at 375 ± 10 nm and visible light 425 ± 20 nm. A high photocatalytic activity was observed for the oxygen-defected ZnO material under visible light illumination compared to the other two materials.

Semi-insulating (Cd,Mn)Te crystals are believed to be suitable to successfully replace the commonly used (Cd,Zn)Te and CdTe crystals as a material for manufacturing large-area X- and γ-ray detectors. The purpose of the studies was to elaborate the technology of the (Cd,Mn)Te crystal plates with high resistivity, uniform in the whole volume of the plate. The article presents a method of annealing of the monocrystalline (Cd,Mn)Te crystal plates, giving the desired, repeatable results. The semi-insulating (Cd,Mn)Te crystals, doped (for compensation) mainly by vanadium, but sometimes by Cl, In, or Cl and V, were grown by the Bridgman method, and the monocrystalline plates were cut. Subsequently the plates were annealed in Cd vapour. The resistivity of the plates was around 109 Ωcm, and the μτ-product was about 10-4 -10-3 cm2/V. Mapping of the resistivity was performed on both the as-grown crystals and the annealed crystal plates. The resistivity of the as-grown crystals was in the range of 105-106 Ωcm and inhomogeneous. After annealing the resistivity increased up to 109 Ωcm and better homogeneity could be seen. Annealing in the saturated Cd vapour influenced tellurium inclusions/precipitates. It was studied by IR transmission microscopy. For the as-grown samples the density of Te inclusions (>1 µm) was ≈ 4×105 cm-3, but for the annealed samples it was ≈ 104 cm-3. The low-temperature photoluminescence (PL) measurements indicated significantly lowered concentrations of acceptors after annealing. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Magnetic anisotropy of (Ge,Mn)Te semiconductor layers exhibiting carrier-induced ferromagnetism was experimentally studied by ferromagnetic resonance (FMR) method. The one micron-thick monocrystalline (Ge,Mn)Te layers were grown on diamagnetic BaF2 (111) substrate by molecular beam epitaxy technique. The analysis of the angular dependence of the FMR resonant field carried out for the external magnetic field direction varying in the (1-10) and (11-2) crystal planes revealed the usual in-plane location of the magnetization easy axis for the Ge0.8Mn0.2Te layer with the cubic structure whereas the normal to the layer plane easy axis was found for the rhombohedral Ge0.9Mn0.1Te layer. These experimental findings are theoretically discused employing group-theoretical methods for various crystal structures as well as density functional theory (DFT) calculations of magnetization dependent contribution to the total electronic energy of (Ge,Mn)Te supercell composed of 64 atoms with Mn substituting Ge at fcc cation sublattice sites. The DFT calculations of (Ge,Mn)Te show an order of magnitude increase of uniaxial magnetic anisotropy in the rhombohedrally distorted layer as compared to the cubic one.

Resonant photoemission spectroscopy was applied to compare the valence band structure of Ge 0.9 Mn 0.1 Te and GeTe semiconductor layers deposited on BaF 2 substrate in monocrystalline and amorphous forms. In (Ge,Mn)Te the contribution of Mn 3 d 5 electronic orbitals to density of states was found in three binding energy regions: below the top of the valence band ( E b p – d hybridization effects, important for magnetic and optical properties of (Ge,Mn)Te, are stronger in monocrystalline than in amorphous (Ge,Mn)Te layers.

Temperature and magnetic eld dependence of magnetization of EuS SrS multilayers grown epitaxially on KCl (001) substrate is experimentally studied by superconducting magnetometry technique. In these lattice-matched semiconductor heterostructures EuS layers are ferromagnetic quantum wells whereas SrS layers are nonmagnetic spacer barriers. The multilayers composed of EuS layers with thickness 3.5 5 nm and SrS layers (thickness 0.5 10 nm) exhibit ferromagnetic transition at 17 K. In the multilayers with ultrathin SrS spacers (0.5 1 nm) a nonmonotonic temperature dependence of magnetization as well as a characteristic switching in magnetic hysteresis loops is observed. These experimental ndings are explained considering antiferromagnetic interlayer coupling between ferromagnetic EuS layers via nonmagnetic SrS spacers. The strength of this coupling is determined based on model magnetization calculations.

The physical properties of ferromagnetic dilute magnetic semiconductors and nanocomposites are considered in a wide range of temperatures from 5 to 300 K. The latter have several advantages as spintronic materials with a controlled magnetic structure for weak magnetic field sensors. A characteristic feature of ferromagnetic nanocomposites is the spin-dependent tunneling conductance, which is responsible for the negative and positive magnetoresistance. The magnetoresistive effects have a wide range of applications. In particular, materials with such effects may be used in the development of magnetoresistive memory devices, weak magnetic field sensors, medical diagnostic devices, and other items of electronic equipment.

Magnetic, structural, and electrical properties are reported for ferromagnetic nanocomposites (FMNC) consisting of nanometer size Co ferromagnetic nanoparticles (NP) embedded in Al 2 O 3 dielectric matrix. Co x (Al 2 O 3 ) 100―x FMNC with x = 7.8, 28.2, and 42.2 at.% were obtained in the form of (1―5) μm thick films by modified electron beam physical vapor deposition of Al 2 O 3 and Co vapors condensing on policor substrate at temperatures 100―400°C. Magnetic properties of these FMNC studied by SQUID magnetometry and ferromagnetic resonance (FMR) methods revealed paramagnetic properties for layers with x = 7.8 at.%, superparamagnetic behavior for x = 28.2 at.%, and ferromagnetic state for the highest Co concentration studied x = 42.2 at.%. Temperature dependence of electrical conductivity in FMNC with low Co content was found to follow the Mott law for variable range hopping mechanism. Magnetic field dependence of resistivity revealed a negative magnetoresistance effect. These results confirm the effectiveness of the applied technology for the preparation of Co x (Al 2 O 3 ) 100―x FMNC.

Ferromagnetic transition and magnetic anisotropy was studied by SQUID magnetometry and ferromagnetic resonance (FMR) methods in poly crystalline Ge 1-x Mn x Te (x = 0.085) semiconductor microstructures embedded in an amorphous, insulating, and paramagnetic (Ge,Mn)Te matrix. The microstructures were produced by pulsed laser and electron beam induced local re-crystallization of amorphous layers deposited on insulating BaF 2 substrates. The angular dependence of the FMR resonance field observed below the Curie temperature T C = 70 K of the microstructures is quantitatively described by the analysis of Zeeman and demagnetization contributions to magnetic free energy. Good agreement with experimental results obtained in the case of structures produced by pulsed laser re-crystallization indicates the formation of ferromagnetic (Ge,Mn)Te thin disks of submicron dimensions.

MBE growth conditions, SEM and XRD structural characterization and experimental studies of optical properties are presented for Pb 1− x Eu x Te/CdTe semiconductor heterostructures grown on GaAs (0 0 1) substrate with a thick CdTe buffer layer. Photoluminescence excited by pulsed YAG:Nd laser was studied in the mid-infrared spectral region for 12.5 nm-thick Pb 1− x Eu x Te quantum wells ( x =0–0.038) with 75 nm-thick CdTe barriers. Increasing the Eu content up to about 4 at% permitted large infrared photoluminescence tuning from 0.34 to 0.465 eV due to the increase in Pb 1− x Eu x Te bandgap.

The valence band structure along the Γ-T and T-W-L directions in the Brillouin zone of GeTe is studied by means of angle-resolved photoemission and compared with the results of ab initio pseudopotential calculations. For Ge1−xMnxTe surface alloy, changes in the valence band induced by presence of Mn atoms are revealed.

This article reports on the structure of the glassy system x CuO–65TeO 2 –(35− x )V 2 O 5 , 5≤ x ≤10 mol% which was studied using infrared (IR) and Raman spectroscopy methods as well as magnetic susceptibility measurements. IR and Raman spectroscopy analysis reveals the presence of four main absorption bands attributed to [TeO 3 ], [TeO 4 ], [VO 4 ], and [VO 5 ] structure units. It suggests that Cu 2+ ions occupy the available open spaces of the Te–O network without straining the bonds too much. Increasing the concentration of Cu 2+ ions beyond 5 mol% results in the modification of the glass by straining and locally distorting the surrounding of the Te–O network. The magnetic susceptibility of these materials was investigated in the temperature range of 5–200 K revealing the paramagnetic behavior described by the Curie–Weiss law and indicating the presence of weak antiferromagnetic exchange interactions between Cu ions. The magnetic entropy change of the glasses was determined based on the temperature and magnetic field dependence of magnetization.

The electronic structure of polycrystalline Ge 0.86 Mn 0.14 Te—ferromagnetic semiconductor with T C =110 K, has been studied by means of resonant photoemission spectroscopy for photon energies close to the Mn 3p→3d excitation. The contribution of Mn 3d states to the electronic structure of the system was revealed and position of the Mn ions in the crystal, characteristic of GeTe-based diluted magnetic semiconductors was proved.

Chemical and phase composition, magnetic susceptibility, SIMS, magnetic force microscopy, and neutron diffraction data for Ge1−x−ySnxMnyTe, InSe⟨Mn⟩, and ZnO⟨Co, Mn⟩ single crystals are investigated over a wide range of temperatures and magnetic fields. For Ge1−x−ySnxMnyTe the existence of ferromagnetic (FM) ordering with a Curie temperature TC∼50K, due to an indirect exchange interaction between Mn ions via the degenerate hole gas, is established. It is shown that at T

EuS/Co multilayers are hybrid structures composed of a model ferromagnetic semiconductor EuS (Curie temperature Tc=16.5 K) and a ferromagnetic transition metal Co. Recent investigations of these multilayers revealed variety of important spintronic effects, such as an antiferromagnetic interlayer coupling in EuS/Co bilayers [1] and a very efficient spin filtering by EuS electron barrier in Al/EuS/Co tunneling structures [2]. These effects are expected to originate from the exchange interactions across EuSCo interface. In previous studies, polycrystalline or amorphous EuS/Co multilayers were grown on glass or on Si substrate with Pt/Co metallic buffer layer. In this work, we exploit the technological method developed for the epitaxial growth of EuS/PbS multilayers on KCl and BaF2 substrates, in order to study the magnetic properties of EuS/Co multilayers with monocrystalline EuS layer. EuS/Co/EuS trilayers and Co/EuS bilayers were grown on cleaved KCl (001) and BaF2 (111) substrates using high vacuum deposition technique employing electron guns for Co and EuS. Epitaxial 20-60 nm thick PbS buffer layer was deposited on the substrates from heated tungsten boat. The layer thickness covered the range 35-55 A for EuS and 40-250 A for Co. The structural properties of the layers were examined by xray diffraction method revealing monocrystalline PbS buffer and bottom EuS layer. Co and top EuS layers are expected to be polycrystalline. Magnetic properties of the layers were examined using magneto-optical Kerr (MOKE) and superconductor (SQUID) magnetometry techniques. In the case of MOKE experiments, the linearly polarized light from He-Ne laser was used in longitudinal MOKE geometry. Measurements of magnetic hysteresis loops were performed in temperature range T = 4-250 K and in external magnetic fields up to 2 kOe applied in the plane of the multilayer. All the investigated multilayers showed ferromagnetic properties at room temperature due to Co layer with the ferromagnetic transition in EuS layer clearly marked upon cooling below 16 K. In EuS/Co/EuS trilayers grown on KCl substrate the antiferromagnetic alignment of magnetization vectors of Co and EuS layers was experimentally observed as a characteristic low field plateau on magnetic hysteresis loops and a decrease of multilayer magnetization below 16 K. In contrast, no interlayer coupling was found in multilayers grown on BaF2 substrate. In Co/EuS bilayers, the characteristic temperature dependent shift of the magnetic hysteresis loops was found indicating the well known exchange bias effect. We assign this experimental finding to the exchange coupling between Co layer and an ultrathin (about 2 nm) top antiferromagnetic CoO layer known to spontaneously form on Co layers in the air.

The accessibility of very efficient light sources in the mid-infrared region is crucial for many applications in medicine, environmental protection or molecular spectroscopy. In this spectral region low dimensional structures based on IV-VI semiconductors like PbTe, are attractive candidates for room temperature operating optoelectronic devices. Recently, high crystal and optical quality PbTe/CdTe multilayers were successfully grown by molecular beam epitaxy on GaAs substrates. These semiconductor materials exhibit excellent matching of their lattice parameters but crystallize in different cubic lattice: zinc blende (a0=6.48 A) for CdTe and rock salt (a0=6.46 A) for PbTe. In PbTe/CdTe heterostructures, narrow gap PbTe constitutes quantum well or quantum dot material with wide gap CdTe electronic barriers. The aim of this work is to determine the optimal conditions for epitaxial growth of PbTe/CdTe structures and to experimentally study their basic optical properties. Various PbTe/CdTe multilayers (superlattices, trilayers) were grown by molecular beam epitaxy using compound PbTe and CdTe sources. Two substrates, i.e. semi insulating (100) oriented GaAs with 4 μm thick high quality CdTe buffer layer and (111) oriented BaF2 with PbTe buffer were used. The structures were deposited at substrate temperature varying in the range 250-340 °C. The layer thickness covered the range t=6-1000 nm for PbTe layers and d=7-500 nm for CdTe barriers. The growth was controlled in-situ by reflection highenergy electron diffraction (RHEED) indicating well defined streaky pattern characteristic for 2D growth mode. After growth, in-situ and ex-situ annealing of samples was performed. The crystal quality of the layers was examined by x-ray diffraction method and cross-sectional observation using atomic force microscopy (see Fig.1). The samples were optically characterized at LHe, LN2 and room temperatures by a photoluminescence measurements using 532 and 1064 nm lines of YAG: Nd pulsed laser for excitation. For both GaAs and BaF2 substrates the best crystal quality of PbTe/CdTe multilayers was obtained for samples grown at relatively low temperatures about 250 °C. The PbTe/CdTe superlattices exhibit in xray spectra diffraction satellites up 4 order. In PL spectra, for excitation by 532 nm, we observe strong luminescence at about 0.8 μm deriving from CdTe and, for excitation by 1064 nm line, broad luminescence with maximum at 3.6 μm from PbTe. In the case of CdTe the photoluminescence is related to neutral acceptor bond excitons, whereas in the case of PbTe we attribute the luminescence to band to band transitions. In IR region we have observed the dependence of luminescence energy (blue shift) on the PbTe layer thickness due to quantum size effect. For thin PbTe layer structures the strong influence of post-growth annealing on luminescence was also find out. Fig.1 Cross–sectional AFM image of the PbTe/CdTe

We present the results of the electronic band structure study of the Ge0.9Mn0.1Te epilayers, clean and modified in situ by deposition of manganese atoms under ultra high vacuum conditions. Ge1-xMnxTe is a ferromagnet with a relatively high Curie temperature (up to 140 K) strongly depending on Mn concentration [1]. Thus, investigation of its properties, including the band structure, attracts considerable interest, in view of possible applications of IV-VI-based systems in fabrication of spintronic devices. The Ge0.9Mn0.1Te layers were grown on BaF2 (111) substrates by an MBE method with use of effusion cells as GeTe, Te2 and Mn solid sources. The substrate temperature was 400-450 o C. The content of Mn in Ge0.9Mn0.1Te was checked by energy dispersive X-ray fluorescence analysis. The sample surface was protected by a layer of amorphous tellurium. Prior the photoemission experiments, the tellurium layer was removed by annealing. The Mn overlayers were deposited in situ at room temperature. The valence band and shallow core levels of Ge0.9Mn0.1Te and ultrathin Mn overlayers have been investigated by means of resonant photoemission spectroscopy (RPES). In this technique the radiation energy is tuned to the intra ion transition (like Mn 3p-3d) in order to enhance emission from partly occupied shells of transition metal atoms. Sets of resonant photoemission spectra were measured for the photon energy range covering the energy of the Mn 3p→3d transition (40

Zinc oxide nanopowders doped with 1–15 mol % cobalt were produced by the microwave solvothermal synthesis (MSS) technique. The obtained nanoparticles were annealed at 800 °C in nitrogen (99.999%) and in synthetic air. The material nanostructure was investigated by means of the following techniques: X-ray diffraction (XRD), helium pycnometry density, specific surface area (SSA), inductively coupled plasma optical emission spectrometry (ICP-OES), extended X-ray absorption fine structure (EXAFS) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and with magnetometry using superconducting quantum interference device (SQUID). Irrespective of the Co content, nanoparticles in their initial state present a similar morphology. They are composed of loosely agglomerated spherical particles with wurtzite-type crystal structure with crystallites of a mean size of 30 nm. Annealing to temperatures of up to 800 °C induced the growth of crystallites up to a maximum of 2 μm in diameter. For samples annealed in high purity nitrogen, the precipitation of metallic α-Co was detected for a Co content of 5 mol % or more. For samples annealed in synthetic air, no change of phase structure was detected, except for precipitation of Co3O4 for a Co content of 15 mol %. The results of the magentometry investigation indicated that all as-synthesized samples displayed paramagnetic properties with a contribution of anti-ferromagnetic coupling of Co–Co pairs. After annealing in synthetic air, the samples remained paramagnetic and samples annealed under nitrogen flow showed a magnetic response under the influences of a magnetic field, likely related to the precipitation of metallic Co in nanoparticles.

In nanocomposite layers consisting of Co nanoparticles in Al2O3 matrix the thermoelectric power was studied in a wide range of Co content. These layers revealed the giant thermoelectric power in a magnetic field for Co content below percolation threshold. This unusual phenomenon has been explained by hopping electron transport through the media which consist of both, nonmagnetic and magnetic centers in the conditions of temperature gradient.

The single fiber transverse compression test (SFTCT) is applied to KEVLAR and TWARON poly (para-phenyleneterephthalamide) fibers, both continuous filament and staple, and of varying denier and heat-treatment, as well as M5 rigid-rod fibers. Resulting force-deflection curves are analyzed by a Hertzian contact model, to give the effective transverse modulus, and estimate the stress state in the fiber at the onset of yield. Confocal microscopy and finite element simulation are used in conjunction with SFTCT to describe the inelastic, transverse deformation of PPTA. The effects of skin-core structure and anisotropy in the fiber cross-section are discussed.

We report on the transverse compression testing of fine,highly anisotropic polymer fibers. Single KEVLAR 29 fibers were laid on a flat, stiff platen, and compressed by a second, stiff, parallel platen. Test output was a force-deflection curve, from which the effective transverse modulus, apparent strain at yield and the work required to compress the fibers were determined. The effects of specimen aspect ratio was examined experimentally and by finite element simulation for loaded fiber lengths of 1/4 to 7 fiber diameters, and a method proposed to deduce the plane strain response from short aspect ratio tests.

It is expected that joint existence of ferromagnetic properties and ferroelectric structural phase transition in diluted magnetic semiconductors IV–VI leads to new possibilities of these materials. Temperature of ferroelectric transition for such crystals can be tuned by the change of Sn/Ge ratio. Magnetic susceptibility, Hall effect, resistivity and thermoelectric power of Ge 1− x − y Sn x Mn y Te single crystals grown by Bridgeman method ( x =0.083–0.115; y =0.025–0.124) were investigated within 4.2–300 K. An existence of FM ordering at T C ∼50 K probably due to indirect exchange interaction between Mn ions via degenerated hole gas was revealed. A divergence of magnetic moment temperature dependences at T ⩽ T C in field-cooled and zero-field-cooled regimes is obliged to magnetic clusters which are responsible for superparamagnetism at T > T C ≈ T f (freezing temperature) and become ferromagnetic at T C arranging spin glass state at T T f ≈ T C . Phase transition of ferroelectric type at T ≈46 K was revealed. Anomalous Hall effect which allows to determine magnetic moment was observed.

We demonstrate an efficient energy conversion in a p-n thermoelectric couple built of bulk Pb0.95Mn0.05Te crystals grown by the Bridgman method and heavily doped n-type with Bi ( n=1.9×1019cm−3) or p-type with Na ( p=2.3×1019cm−3). Substitution of Mn2+ ions for Pb2+ ions at the rock-salt lattice cation sites increases the band gap of Pb1−xMnxTe and decreases the energy separation between the light hole L-band and the heavy hole Σ-band. It results in a large increase of thermoelectric power and improved thermoelectric parameters of p-type Pb1−xMnxTe. Applying the Harman method for samples of various lengths, we experimentally determined the radiation correction factors and found the thermoelectric figure of merit parameter ZT=0.75–0.8 at T=650 K for both n- and p-type materials with good thermoelectric matching of the couple. We report on thermoelectric performance of a p-n thermoelectric couple assembled of these materials and tested over the T=300–670 K temperature region.

In this work we present a comparison of the experimental results, which have been obtained in the resonant photoemission study of electronic structure of epitaxial layers and bulk crystals of GeTe doped with Mn and/or Eu. Narrow-gap IV–VI semiconductors are known to form solid solutions not only with magnetic ions with partially filled 3d shell (e.g. Mn, Fe), but also with the elements with partially filled 4f shell (e.g. Eu, Gd). Such diluted magnetic semiconductors (DMS) exhibit transport, optical and magnetic properties attracting large interest from the point of view of basic research as well as of applications in infrared radiation sources, detectors, thermoelectric generators and, recently, spintronic devices. The ferromagnetic ordering in IV-VI –based diluted magnetic semiconductors (DMS) is governed by the Ruderman–Kittel–Yoshida–Kasuya interaction mediated by free holes related to native defects. Ge

4th Workshop on Quantum Chaos and Localisation Phenomena, Polish Acad Sci, Ctr Theoret Phys, Inst Phys, Warsaw, POLAND, MAY 22-24, 2009; International audience; In this paper the physical properties of two types of Co-doped ZnO nanostructures: tetrapods and nanofibers grown by a rapid thermal evaporation process and prepared by the electrospinning technique. respectively were investigated and analyzed. Surface morphology of the samples was examined using scanning electron microscopy. X-ray diffraction measurements showed hexagonal wurtzite crystal structure of both types of investigated nanostructures. Both X-ray diffraction and Raman scattering data confirmed high phase purity of the samples. The magnetic properties studied with the use of the SQUID magnetometer confirmed a presence of ferromagnetic order in analyzed nanostructures. The observed photoluminescence spectra exhibited two groups of lines. The First one. in the ultraviolet spectral range, is clue to the optical transitions close to ZnO band gap, the second one in the red region is most probably related to the Co(2+) d-d internal transitions. The influence of native defects on the optical properties is also shown and discussed. All results reported here lead us to the conclusion that in the mixed crystal nanostructures obtained, a fraction of the Zn(2+) ions is substituted by Co(2+) ions.

Ferromagnetic Ge1−xMnxTe thin films with x≤0.19 were deposited on (111) oriented BaF2 monocrystals using molecular beam epitaxy technique. X-ray diffraction carried out at high temperatures for samples with x≤0.05 revealed ferroelectric transition from rock-salt to rhombohedral structure at T=625–675 K. The magnetic properties investigated with SQUID magnetometry and ferromagnetic resonance technique exhibit an easy magnetization direction normal to the plane in as grown samples. We attribute this finding to lattice strain due to mismatch of thermal expansion coefficients or to the crystalline stress related to inhomogeneous distribution of Mn ions in the sample volume. Thermal treatment changes the easy axis into in-plane direction which can be associated with distinct improvement of the structural properties.

The structural and electrical properties of Pb1−yGeyTe and Pb1−x−yGeyEuxTe (0≤y≤0.4 and x≤0.05) monocrystalline layers grown by molecular beam epitaxy technique on BaF2 (111) substrate were studied by X-ray diffraction, Hall effect, and electrical conductivity measurements. Based on the temperature dependence of the lattice parameter the structural (ferroelectric) transition temperature was found in the temperature range before 100 to 250 K in layers with varying Ge and Eu content. Electrical measurements indicates that incorporation of Eu ions in the PbGeTe crystal matrix decreases the electrical conductivity in p-type PbGeEuTe layers by 1–2 orders of magnitude.

Ferromagnetic resonance (FMR) study of magnetic anisotropy is presented for thin layers of IV-VI diluted magnetic semiconductor Ge1-xMn xTe with x=0.14 grown by molecular beam epitaxy (MBE) on KCl (001) substrate with a thin PbTe buffer. Analysis of the angular dependence of the FMR resonant field reveals that an easy magnetization axis is located near to the normal to the layer plane and is controlled by two crystal distortions present in these rhombohedral Ge1-xMnxTe layers: the ferroelectric distortion with the relative shift of cation and anion sub-lattices along the [111] crystal direction and the biaxial in-plane, compressive strain due to thermal mismatch.

The authors have completed their institutions to properly reflect the contributions of the affiliated institutions.

Magnetic susceptibility and electron paramagnetic resonance (EPR) have been measured in epitaxial layers of Cd1−x−yZnxMnyTe. This magnetic quaternary alloy, similarly to the non‐magnetic ternary alloy Cd1−x ZnxTe, exhibits bistable resistance and ferroelectric properties at the room temperature. We show that the magnetic properties of Cd1−x−yZnxMnyTe depend of the resistance state of the material. The effect is explained by a changing of magnetic coupling between the neighboring Mn atoms from antiferromagnetic to ferromagnetic. By first principle calculations we show that the ferromagnetic coupling is mediated by a presence of a Zn‐interstitial‐vacancy complex in the vicinity of Mn‐Mn pair.