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CdGeAs 2 is a promising material for optical applications. It has the wide transparency range between 2.3 and 18 μm except harmful absorption region at 5.5 μm. Its presence is related to the crystal lattice quality. The measurements of Raman and far infrared reflectivity spectra of the series of Cd 1− x Mn x GeAs 2 samples (0 ≤ x ≤ 0.037) were carried out in spectral range from 60 to 400 cm −1 , at room temperature. Beside all expected optical modes three defect modes are registered at about 125, 170 and 235 cm −1 . Their intensities are related to tetragonal distortion of lattice (Δ) so we connected them with lattice defects Ge As , usually formed in this material, and CdAs 2 and Cd 3 As 2 clusters whose characteristic frequencies match these values. Antisite defects Ge As are connected to energy level at about 200 meV and to absorption at 5.5 μm. Based on obtained results we can conclude that doping with small amount of manganese ( x = 0.004) results in slight deformation of CdGeAs 2 crystal lattice and consequently considerably reducing the formation of antisite defects Ge As .

We present studies of the influence of the chemical composition changes on the type of magnetic order present in bulk nanocomposite Ge 1− x−y Pb x Cr y Te crystals with the average Pb-content close to x ≈ 0.20 and Cr-content, y , varying from y = 0.017 up to 0.043. Detailed magnetometric studies revealed the existence of two ordered magnetic states present in all our samples. All our crystals show a paramagnet to spin-glass-like state transition at temperatures from 135 K to 145 K, related to the presence of Cr 5 Te 8 clusters in the host lattice. The second transition type depends on the Cr-content, y . In the case of samples with y equal to 0.038 and 0.043 the ferromagnetic phase is observed with T C slightly below 70 K, while in samples with lower chromium concentration the presence of spin-glass-like state slightly below 50 K is observed. The presence of clusters in our samples has significant impact on the carrier transport and magnetotransport in our samples. The presence of critical scattering on the magnetic impurities is observed in resistivity and magnetoresistance data. Nearly-linear magnetoresistance is also observed in our samples indicating a presence of strong scattering on the grain boundaries in our samples.

We present studies of magnetotransport properties of Ge 1− x − y Pb x Mn y Te bulk crystals with chemical composition changing from 0.180 x y T SG around 90 K. The presence of strong anomalous Hall effect (AHE) with hysteresis is observed at T T SG . The data analysis allowed calculation of a correction to the Hall constant R H for T T SG and the AHE constant, R S . R S is around 10 −6 m 3 /C. R S and R H do not change strongly with temperature. The scaling law analysis has proved that the AHE in this system is due to the extrinsic mechanisms dominated by the skew scattering with relatively small contribution of the side jump process. Strong localization occurs in our system at T T SG and causes a presence of a minimum in the resistivity vs. temperature dependence. The magnetoresistance of our samples shows complex behavior at T T SG . The negative magnetoresistance is observed at T T nearly linear positive magnetoresistance is observed at temperatures from 20 K up to T ≈ T SG , where it reaches maximum. Positive linear magnetoresistance is related to the granular nature of our samples while the maximum near T SG is related to the giant spin-splitting of the valence band.

We present the studies of structural, electrical, and magnetic properties of bulk Sn 1 − x − y Cr x Eu y Te crystals with different chemical compositions varying in the range of 0.004 ≤ x ≤ 0.089 and 0.007 ≤ y ≤ 0.020. The structural characterization of our samples indicated the clustering of the Cr-ions into Cr–Te related clusters. Eu ions do not form clusters and are randomly distributed in the SnTe lattice. The magnetotransport studies show the presence of positive linear magnetoresistance with maximum amplitude of about 80% for all our samples. Positive magnetoresistance is a geometrical effect related to the presence of clusters in the SnTe lattice. The cluster-glass-like state at the temperature of about 130 K is observed for x ≤ 0.025. The cluster-glass-like state is due to the presence of Cr-rich clusters in the SnTe lattice. The ferromagnetic behavior with the Curie temperature of about 275 K is observed for the samples with x > 0.077 indicating the presence of Cr 5 Te 8 clusters in the host material. Eu ions presence in our samples shows paramagnetic behavior.

We present studies of magnetic properties of Ge 1− x − y Pb x Mn y Te bulk crystals with chemical composition varying in the range of 0.180 x y J pd , having values from 0.47 eV to 0.80 eV gives spin-glass transition temperature, T SG , values close to the experimental values for the Ge-rich phase. The magnetic order observed for the Pb-rich phase is also due to the carrier mediated magnetic interaction. The experimental transition temperatures are fitted with J pd value ranging from 0.22 eV to 0.28 eV.

Three self-assembled nanogranular composites based on MnAs ferromagnetic inclusions embedded in ZnSnAs 2 semiconductors with MnAs concentration 10, 20, 47 mol.% were synthesized. The samples were studied by X-ray, SEM, AFM, MFM and SQUID methods. It has been shown that the increasing of the MnAs concentration in composite leads to slightly increasing of the size of the magnetic inclusions. Their size depends mainly on the speed of the crystallization, but the shape of the inclusions depends on the type of the interaction between materials. The connection between equilibrium and non-equilibrium structure of the compounds has been demonstrated. Magnetic properties of the ZnSnAs 2 + MnAs samples show ferromagnetic phase transition with the Curie temperature having values from 313 K to 336 K, increasing as a function of the MnAs concentration in the nanocomposite. A small paramagnetic signal is observed at low temperatures due to individual Mn ions randomly distributed in the ZnSnAs 2 lattice. All our samples show only a narrow magnetic hysteresis loop except of the sample with 47 mol.% of MnAs, for which the coercive field increases to about 120 G. The carrier transport of the alloy shows significant influence of the MnAs clusters. All our samples have p-type conductivity with magnetotransport strongly influenced by the presence of the MnAs phase in the nanocomposite samples. The magnetoresistance (MR) of the alloy shows a complex behavior. The grain boundaries and MnAs clusters influence on the amplitude, sign, and temperature of MR.

The interest in thorough description of Zn 1– x Mn x GeAs 2 arises from its suitability for application in the field of non-linear optics. The room temperature far-infrared reflectivity spectra of single crystals Zn 1– x Mn x GeAs 2 , where 0 ≤ x ≤ 0.078, were measured in the spectral range from 80 cm −1 to 500 cm −1 . The spectra were analyzed by fitting procedure using a dielectric function which includes interaction between a plasmon and two different phonons. The detected phonons are in excellent agreement with the theoretical predictions. The MnAs cluster phonons are detected, as well.

The aim of the present work is to study the magnetic properties of ZrO2(Fe) nanocrystals prepared by the wet chemistry method. The microwave assisted hydrothermal synthesis was used. The detailed structural characterization was performed by means of X-ray diffraction and TEM studies. 57 Fe Mossbauer spectra were recorded at room temperature for all samples. The isomer shift and quadrupole splitting indicate the presence of Fe 3+ ions. The systematic measurements of AC magnetic susceptibility up to 350 K and magnetization as a function of magnetic field (up to 9 T) and temperature were performed. Depending on the nominal concentration of magnetic dopant different types of magnetic behavior, were observed. 2015 Elsevier B.V. All rights reserved.

The phase equilibria in the ZnGeAs 2 –CdGeAs 2 system were investigated by X-ray, DTA, EDXRF, microstructure observations and SEM. The solid solutions are present in all range of concentrations above 440 °С. Below this temperature a decay region of solid solution of Zn 1− x Cd x GeAs 2 is observed in the range of concentrations x = 0.19–0.92 at room temperature. The investigation of the system was obstructed by liquation and segregation processes occurring during the synthesis.

Nanocrystalline samples of ZnO(Mn) were characterized by X-ray diffraction to determine composition of the samples (ZnO, Mn3O4, ZnMn2O4 and ZnMnO3) and the mean crystalline size (between 9 and 13 nm for ZnMnO3 phases, from 24 to 47 nm for Mn3O4 phases and above 100 nm for ZnO and ZnMn2O4 phases). In this paper we report the experimental spectra of Raman scattering (from 200 to 1600 cm−1) with surface optical phonons (SOP) in range of 520–575 cm−1. The phonon of registered phases exhibits effects connected to phase concentration, while the SOP phonon mode exhibits significant confinement effect.

The properties of 3 monolayers (ml) CdTe self-assembled quantum dot (SAQD) sample are investigated by means of Raman and photoluminescence (PL) spectroscopy. The PL spectrum is characterized by two main emission peaks, both connected with the existence of QDs. One presents direct deexcitation to ground state and the other one is optical phonon ( ω = 204.2 cm −1 ) assisted deexcitation. One-phonon Raman spectra at room temperature show surface-optical phonon at 201 cm −1 . At temperatures below 200 K, multiphonon processes are registered. Multiphonon maximum depends on the temperature, and laser energy.

The aim of the present work is to study the magnetic properties of nanocrystals of ZnO(Co) prepared by two methods of synthesis. We used the microwave assisted hydrothermal synthesis and traditional wet chemistry method followed by calcination. The detailed structural characterization was performed by means of X-ray diffraction and micro-Raman spectroscopy measurements. The magnetic properties were studied by means of AC susceptibility χ. All samples demonstrated Curie–Weiss behavior at higher temperatures. For calcination process, the negative values of the Curie–Weiss θ temperature were observed indicating the predominance of antiferromagnetic interactions. For samples prepared by hydrothermal synthesis, we observed the breakdown of predominance of antiferromagnetic interactions.

Surface optical phonons (SOP) were observed in the range of 496–572 cm−1 on Raman scattering spectra of nanocrystalline samples of ZnO(Co) prepared by use of the microwave assisted hydrothermal synthesis and traditional wet chemistry method followed by calcinations. The phase composition of the samples (ZnO, Co3O4, ZnCo2O4) and the mean crystalline size (14–300 nm) were determined using X-ray diffraction measurements. The SOP phonon mode exhibit significant size confinement effect, while the phonons of registered phases exhibit effects connected to phase concentration.

The aim of the present work is to study the magnetic properties of ZnO(Fe) nanocrystalline samples prepared by two methods of synthesis. We have used the microwave assisted hydrothermal synthesis and traditional wet chemistry method followed by calcination. The detailed structural characterization was performed by means of X-ray diffraction and micro-Raman spectroscopy measurements. The dynamic magnetic properties were studied by means of AC susceptibility χ . The measurements were performed at small AC magnetic field with amplitude not exceeding 5 Oe and different frequency values (from 7 Hz to 9970 Hz). The AC susceptibility maxima have been found for in-phase susceptibility Re ( χ ) and for out of phase susceptibility Im ( χ ). We analyzed the observed frequency dependence of the peak temperature in the AC susceptibility curve using the empirical parameter Φ that is a quantitative measure of the frequency shift and is given by the relative shift of the peak temperature per decade shift in frequency, as well as Vogel–Fulcher law.

We have synthesized CdS and Cd0 7Mn0 3S nanocrystals with diameters of about 45 nm These materials have been studied using photoluminescence spectroscopy with various excitation energies in the temperature range from 1 8 to 300 K We registered surface and defect states as well as two Mn2+ energy levels that correspond to Mn2+ ions in two different crystal environments. In addition, the resonant behavior of one Mn state excited by 514.5 nm wavelength of laser light has been clearly observed in obtained spectra We proposed the scheme of energy levels and transitions that explain obtained experimental results (C) 2010 Elsevier B V. All rights reserved

We fabricated a simple magnetoresistive microdevice formed by a narrow constriction of submicron width in the epitaxial film of a ferromagnetic (Ga,Mn)As semiconductor, and investigated magnetic properties of the film and the low-temperature charge-carrier transport through the constriction. We have revealed sharp jumps of a lowered conductance in a non-constricted sample and jumps of an enhanced conductance in the constricted one, which appeared when the sweeping magnetic field crossed the regions of the coercive field of the film. We argue that the both features result from a contribution of a magnetic domain wall to the conductance. While the spin-orbit interaction can be responsible for the negative contribution of a domain wall to the conductance, presumably the suppression of the weak localization effects by a domain wall located in the constriction results in the positive contribution to the conductance.