I. Svito

Influence of the short-range order in FeCoZr nanoparticles on the electrical and magnetotransport properties of FeCoZr-CaF2 nanocomposites

This paper reports on the results of the 57Fe Mössbauer investigation of the short-range order in FeCoZr nanoparticles and also the studies of the electrical and magnetotransport properties of (FeCoZr)x(CaF2)100 − x granular nanocomposite films in the concentration range x = 16–75 at %. A correlation between the oxygen partial pressure during the synthesis of nanocomposites and the magnetic state of iron-containing nanoparticles has been established. The influence of the oxidation of metallic particles on the electron transport mechanisms and on the magnetoresistance of the films has been analyzed. It has been found that, in the nanocomposites with a high FeCoZr concentration (x ∼ 70–75 at %), there is a preferred orientation of the magnetic moments of α-FeCo(Zr) nanoparticles in the direction perpendicular to the film plane.

Electric properties of composite ZnO-based ceramics doped with Fe

This work is focused on the analysis of phase structure and temperature dependences of electric resistivity ρ(Т) in ZnO-based composite ceramics (ZnO)90(FexOy)10, doped with Fe by the addition of 10 wt.% of one of the iron oxides FexOy. Streszczenie. Praca koncentruje się na analizie struktury fazowej oraz zależności temperaturowych rezystywności elektrycznej ρ(Т) kompozytów ceramicznych (ZnO)90(FexOy)10 opartych o ZnO, domieszkowanych Fe poprzez dodanie 10% wag. jednego z tlenków żelaza FexOy. (Własności elektryczne ceramiki kompozytowej na bazie ZnO domieszkowanej Fe)

Synthesis and properties of doped ZnO ceramics

In our work, we studied zinc oxide ceramic samples doped with aluminum and gallium. Structure peculiarities of ceramics depending on their synthesis regime were investigated by the SEM, EDX, XRD, and Raman spectroscopy methods. It was demonstrated that at some technological conditions the formation of indesirable phases of zinc aluminate or gallate may occur preventing an uniform material doping and reducing quality of samples. Single-phase ZnO ceramics were produced when the nanostructured alumina powders were used as a dopant source. The correlations between the synthesis regimes of ZnO ceramics and their electrophysical parameters essential for thermoelectric figure-of-merit (electrical conductivity and Seebeck coefficient) have been established. The best electrophysical characteristics were obtained when the nanostructured alumina produced by combustion in isopropyl alcohol was used as a dopant. Conductivity and Seebeck coefficient of such ceramics are equal to 3·10 S/m and -0.27 mV/K, respectively, corresponding to the power factor of 2.2·10 W/(m·K). Streszczenie. W naszej pracy zbadaliśmy próbki ceramiki tlenku cynku domieszkowanej aluminium oraz galem. Specyfikę struktury ceramiki zależącą od warunków syntezy zbadano metodami SEM, EDX, XRD oraz spektroskopią Ramana. Zaprezentowano, że dla niektórych warunków technologicznych tworzą się niepożądane fazy glinianu cynku lub galusanu zapobiegając jednolitemu domieszkowaniu materiału oraz zmniejszając jakość próbek. Jednofazowa ceramika ZnO została uzyskana w czasie, gdy nanostrukturalny proszek tlenku aluminium był używany jako źródło domieszki. Określono powiązania pomiędzy warunkami otrzymywania ceramiki ZnO oraz jej elektro-fizycznymi parametrami niezbędnymi do termoelektrycznego współczynnika jakości (przewodnictwo elektryczne oraz współczynnik Seebeck`a). Najlepsze elektrofizyczne charakterystyki otrzymano, gdy używano jako domieszkę nanostrukturalny tlenek aluminium produkowany poprzez spalanie w alkoholu izopropylowym. Przewodność oraz współczynnik Seebeck`a tego typu ceramik wynosi odpowiednio 3·10 S/m oraz -0.27 mV/K, co odpowiada współczynnikowi mocy równemu 2.2·10 W/(m·K). (Synteza i właściwości domieszkowanej ceramiki ZnO).

Low-temperature conductivity of silicon doped with antimony

A detailed analysis of the experimental temperature dependences of the resistivity of silicon doped with arsenic with a concentration of 1018 cm−3 is performed for the region 1.8 K < T < 25 K. It is shown that, as a result of cooling to a temperature lower than 4.5 K, a transition from the Mott mode with variable hopping length to the mode of hopping conduction via nearest neighbors is observed, while, at T < 2.5 K, a transition to the Shklovskii-Efros mechanism is possible. A model for such a temperature crossover is suggested; the model is based on simplified solution of the percolation problem with the use of an interpolation expression for the density of states. Performed estimates show that the model is in satisfactory agreement with experimental data when the minimum number of adjustable parameters are used.

Ion Irradiation of Oxidized FeCoZr-CaF2 Nanocomposite Films for Perpendicular Magnetic Anisotropy Enhancement

Ion Irradiation of Oxidized FeCoZr–CaF2 Nanocomposite Films for Perpendicular Magnetic Anisotropy Enhancement J. Kasiuka,∗, J. Fedotova, J. Przewoźnik, C. Kapusta, V. Skuratov, I. Svito, V. Bondariev and T.N. Kołtunowicz Institute for Nuclear Problems of Belarussian State University, 220030 Minsk, Belarus AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Department of Solid State Physics, al. Mickiewicza 30, 30-059 Krakow, Poland Joint Institute for Nuclear Research, 141980 Dubna, Russia Belarusian State University, 220030 Minsk, Belarus Department of Electrical Devices and High Voltage Technology, Lublin University of Technology, Nadbystrzycka 38A, 20-618 Lublin, Poland

Enhanced magnetoresistive effect in the arrays of nickel nanorods on silicon substrates

It is shown that the magnetoresistive properties of n–Si/SiO2/Ni, nanostructures containing nanogranular nickel rods in a SiO2 layer’s vertical pores substantially differ from the similar properties in the earlier studied nanogranular Ni films electrodeposited onto the n–Si plates. From the point of view of the electrophysical properties, the nanostructures studied are analogous to a system of two Schottky Si/Ni diodes, which are connected to each other. The magnetoresistance of such structures has been studied in the temperature range from 2 to 300 K and the magnetic field range of up to 8 Tl. It is established that at temperatures of 17–27 K the structures possess a positive magnetoresistive effect, whose value depends on the transverse voltage applied to the structure and increases with a decrease in the longitudinal (along the rods) current intensity. At a current of 100 nA, the relative magnetoresistance in the field of 8 Tl increases from 500 to 35000% by an increase in the transverse voltage from 0 to–2 V. The observed magnetoresistive effect is associated with the influence of the magnetic field on the processes of impact ionization of impurities resulting in an avalanche breakdown of the Ni/Si Schottky barrier. Thus, the possibility of controlling the magnetoresistive effect in n–Si/SiO2/Ni template structures by applying an additional (transverse) electric field to the nanostructure between the silicon substrate (as the third electrode) and nickel rods is proven.