Electrical and galvanomagnetic properties of AuAl2+6%Cu intermetallic compounds at low temperatures

The AuAl2 intermetallic compounds are of substantial interest in view of their application potential. The investigated intermetallics AuAl 2+6%Cu were prepared from fine powders of AuAl2 and Cu by vacuum sputtering on a glass substrate and consisted of films with a thickness of about one micrometer. The films were annealed. The temperature and field dependence of the electroresistivity, the magnetoresistivity and the Hall effect of AuAl2+6%Cu films were measured in the temperature interval from 4.2 to 100 K and at magnetic fields of up to 15 T. We demonstrate that the temperature dependence of the electroresistivity has a minimum at T = 20 K and a metallic behavior above this temperature. The magnetoresistivity is very small (less then 1%), positive at low temperatures and negative above 12 K. The Hall coefficient is positive, which corresponds to the holes in a one zone model with a charge carrier concentration of about 1.6 1020 cm-3. © Published under licence by IOP Publishing Ltd

Specific features of the electrical resistance of half-metallic ferromagnetic alloys Co2CrAl and Co2CrGa

It has been shown by comparing the results of studying the electrical and magnetic properties of the half-metallic ferromagnetic Heusler alloys Co2CrAl and Co2CrGa with the calculations of their electronic structure that high values of the electrical resistivity ρ are caused by a disordered distribution of atoms over the sites of the L21 cubic structure, and the anomalous behavior of ρ(T) is associated with the transformation of the electronic spectrum due to the ferromagnetic-to-paramagnetic transition. © 2013 Pleiades Publishing, Ltd

Magnetic and electrical properties of the half-metallic ferromagnets Co2CrAl

This paper presents the results of measurements of the magnetic and electrical properties of the ferromagnetic alloy Co2CrAl in two structural states: (i) after severe plastic deformation and (ii) after shortterm high-temperature annealing of the deformed specimens. The experiments have been performed at temperatures in the range from 2 to 900 K in magnetic fields H ≤ 50 kOe. The ferromagnetic Curie temperature TC and the paramagnetic Curie temperature Θ have been determined (TC = 305 K and Θ = 326 K), as well as the spontaneous magnetic moment μS and the effective magnetic moment μeff per molecule of the alloy (μS = 1.62 μB and μeff 2 = 8.2 μB 2). It has been shown that the magnetic crystalline anisotropy energy of the alloy is on the order of ∼5 × 105 erg/g. The specific features of the electrical properties are associated with the presence of an energy gap in the electronic spectrum near the Fermi level EF and with the change in the parameters of the energy gap as a function of the temperature. © 2013 Pleiades Publishing, Ltd

Size effect in the electronic transport of thin films of Bi 2 Se 3

Thin films of a topological insulator (TI) Bi 2 Se 3 of various thicknesses from 20 nm to 75 nm were obtained. The resistivity measurements were carried out according to the conventional 4-contact DC technique. This allows to "separate" the bulk and surface conductivities at different temperatures and magnetic fields. It was suggested that similar effects should be observed in other TIs and systems with inhomogeneous distribution of dc-current on sample cross section. © 2018 The Authors, published by EDP Sciences.This work was partly supported by the state assignment of FASO of Russia (theme “Spin” No. ȺȺȺȺ Ⱥ 4 ), by the RFBR (project No. 17-52-52008), by the Government of the Russian Federation (state contract No. 02.A03.21.0006), and by grant of Russian Ministry of Education and Science No 14.Z50.31.0025

Enhancing the smartroom system with e-tourism services

The SmartRoom system is a service-oriented application for assisting such collaboration activity as conference or meeting in a room equipped with computing and presentational devices and Internet access. The development is open source and based on the Smart-M3 platform. In this paper, we consider advanced scenarios for SmartRoom to enhance the latter with e- Tourism services. We introduce a smart space based architecture for this enhancement. We provide an ontology for representing and sharing the tourism-related information for service construction. Based on the architecture and ontology, several case study services are designed. In particular, we implement a service for collaborative construction of a social program for conference participants. The implemented service is integrated into the SmartRoom system and demonstrates the feasibility of the proposed design

Peculiarities of the electronic transport in half-metallic Co-based Heusler alloys

Electrical, magnetic and galvanomagnetic properties of half-metallic Heusler alloys of Co$_2$YZ (Y = Ti, V, Cr, Mn, Fe, Ni, and Z = Al, Si, Ga, Ge, In, Sn, Sb) were studied in the temperature range 4.2--900 K and in magnetic fields of up to 100 kOe. It was found that varying Y in affects strongly the electric resistivity and its temperature dependence $\rho(T)$, while this effect is not observed upon changing Z. When Y is varied, extrema (maximum or minimum) are observed in $\rho(T)$ near the Curie temperature $T_C$. At $T < T_C$, the $\rho(T)$ behavior can be ascribed to a change in electronic energy spectrum near the Fermi level. The coefficients of the normal and anomalous Hall effect were determined. It was shown that the latter coefficient, $R_S$, is related to the residual resistivity $\rho_0$ by a power law $R_S \sim \rho_0^k/M_S$ with $M_S$ the spontaneous magnetization. The exponent $k$ was found to be 1.8 for Co$_2$FeZ alloys, which is typical for asymmetric scattering mechanisms, and 2.9 for Co$_2$YAl alloys, which indicates an additional contribution to the anomalous Hall effect. The temperature dependence of resistivity at low temperatures is analyzed and discussed in the framework of the two-magnon scattering theory.Comment: Invited Report on the Moscow International Symposium on Magnetism MISM-2017, pdf only, 6 pages, J. Magn. Magn. Mater., in pres

Unusual Kinetic Properties of Usual Heusler Alloys

The review considers various groups of Heusler compounds, which can have the properties of a semiconductor, a half-metallic ferromagnet, a spin gapless semiconductor, a topological semimetal, and a non-collinear antiferromagnet. In these Heusler compounds, “conventional” from the point of view of the crystal structure, unusual kinetic and magnetic properties can be observed, which are caused by the features of their electronic structure (e.g., presence of an energy gap for one spin projection) and magnetic state (e.g., strong ferromagnetism, compensated ferrimagnetism). Their magnetic and kinetic characteristics are very sensitive to external influences. Depending on the alloy composition and external parameters, transitions between the considered states can be realized. All this opens up further prospects for controlling the electronic and magnetic characteristics of such compounds and their practical application. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Ministry of Education and Science of the Russian Federation, Minobrnauka: 122021000036–3, 122021000038–7; Russian Science Foundation, RSF: 22–22-00935The research was carried out within the state assignment of Ministry of Science and Higher Education of the Russian Federation (themes “Spin,” No. 122021000036–3 and “Quantum,” No. 122021000038–7). Research funding was provided by the Ministry of Science and Higher Education of the Russian Federation (Ural Federal University Program of Development within the Priority-2030 Program). The Sect. was prepared with the financial support of the Russian Science Foundation within the framework of research project No. 22–22-00935

Peculiarities of Electronic Transport and Magnetic State in Half-Metallic Ferromagnetic and Spin Gapless Semiconducting Heusler Alloys

Abstract: A brief survey of experimental and theoretical studies of half-metallic ferromagnets (HMFs) and spin gapless semiconductors is given, the possible candidates being the X2YZ (X = Mn, Fe, Co; Y = Ti, V, Cr, Mn, Fe, Co, Ni; Z = Al, Si, Ga, Ge, In, Sn, Sb) Heusler alloys. The data on the electrical resistivity, normal and anomalous Hall Effect, and magnetic properties are presented. It is shown that the Co2FeZ alloys demonstrate properties of conventional ferromagnets, the HMF properties being also manifested upon variation of the Z-component. The Fe2YAl and Mn2YAl alloys show upon variation of the Y-component both metallic and semiconducting electronic characteristics, the magnetic properties changing from the ferromagnetic to compensated ferrimagnetic state. The HMF and spin gapless semiconductor states are supposed to exist in these Heusler alloys systems. © 2019, Pleiades Publishing, Ltd

Peculiarities of the electronic and magnetic characteristics in Co2YSi (Y = Ti, V, Cr, Mn, Fe, Co, Ni) Heusler alloys close to the half-metallic ferromagnets and spin gapless semiconductors

The Hall Effect and magnetization of Heusler alloys Co2YSi (Y = Ti, V, Cr, Mn, Fe, Co, Ni) were measured at T = 4.2 K and 300 K in magnetic fields of up to 100 kOe as well as the temperature dependence of the electroresistivity from 4.2 to 300 K. The normal and anomalous Hall coefficients, saturation magnetization, residual resistivity, type and concentration of current carriers and their mobility were obtained. It was demonstrated that there is a clear correlation between the electronic and magnetic parameters obtained, depending on the number of valence electrons z, at the transition from Co2TiSi (z=26) to Co2NiSi (z=32). The observed peculiarities of electronic and magnetic parameters may be due to the appearance of the states of the half-metallic ferromagnet and/or spin gapless semiconductor. © Published under licence by IOP Publishing Ltd.This work was carried out as part of the state task of the Russian Ministry of Education and Science (themes “Spin”,No. AAAA-A18-118020290104-2) with partial support from the Russian Foundation for Basic Research (projects Nos. 18-32-00686 and 18-02-00739) and the Government of the Russian Federation (Act No. 211, contract No. 02.A03.21.0006)