50 research outputs found

    Cluster superconductivity in the magnetoelectric Pb(Fe1/2Sb1/2)O3 ceramics

    Full text link
    We report the observation of cluster (local) superconductivity in the magnetoelectric Pb(Fe1/2Sb1/2)O3 ceramics prepared at a hydrostatic pressure of 6 GPa and temperatures 1200-1800 K to stabilize the perovskite phase. The superconductivity is manifested by an abrupt drop of the magnetic susceptibility at the critical temperature TC 7 K. Both the magnitude of this drop and TC decrease with magnetic field increase. Similarly, the low-field paramagnetic absorption measured by EPR spectrometer drops significantly below TC as well. The observed effects and their critical magnetic field dependence are interpreted as manifestation of the superconductivity and Meissner effect in metallic Pb nanoclusters existing in the ceramics. Their volume fraction and average size were estimated as 0.1-0.2% and 140-150 nm, respectively. The superconductivity related effects disappear after oxidizing annealing of the ceramics.Comment: 9 pages, 5 figure

    Magneto-optical studies of BaFe12O19 films grown by metallo-organic decomposition

    Get PDF
    M-type barium hexagonal ferrites BaFe12O19 (BaM) films considered for new devices that operate in the 40-70 GHz range with small or zero applied magnetic fields were characterized by magneto-optical (MO) complex polar “Kerr” effect (PKE) spectroscopy, MO magnetometry, and spectral ellipsometry (SE). The textured polycrystalline films were grown on Pt(111)/TiO2 template on Si wafer using metallo-organic decomposition technique (MOD) followed by rapid thermal annealing. In the films grown in one, two and three MOD iterations, the thickness was evaluated by SE and transmission electron microscopy. The film thickness ranged from 30 nm to 50 nm per MOD iteration. The best films display out-of-plane effective magnetic anisotropy field of 13 kOe, high perpendicular remanent magnetization and ferromagnetic resonance linewidth of 340 Oe at 60 GHz. The coercivity deduced from the MO hysteresis loops ranged between 0.25 kOe and 0.52 kOe. The SE and PKE spectra were taken at photon energies from 0.7 eV to 6.4 eV and from 1.2 eV to 4.8 eV, respectively. The PKE spectra display the structure observed on BaM single crystal natural faces normal to the c-axis. They are consistent with magnetoplumbite structure, with high degree of grain c-axis ordering, absence of foreign phases and Fe valence-exchange mechanism. Single phase nature of the films was further confirmed by grazing incidence X-ray diffraction and 57Fe nuclear magnetic resonance at 4.2 K.Web of Science561330132

    Automata theory motivated by problem solving

    Full text link

    Study of Y-type Hexaferrite by Means of 57Fe\text{}^{57}Fe NMR and Electronic Structure Calculations

    Full text link
    The electron structure and site preferences of Zn and Fe cations in Y hexaferrite system were calculated. The hyperfine magnetic fields on 57Fe\text{}^{57}Fe nuclei were determined using WIEN2k and corrections for hyperfine contact interaction. The calculated fields were compared to 57Fe\text{}^{57}Fe nuclear magnetic resonance (NMR) experiment in Ba2Zn2Fe12O22Ba_2Zn_2Fe_{12}O_{22} single crystal with an aim of interpretation of experimental NMR spectrum

    Beyond Communication and Control: Environmental Control and Mobility by Gaze

    Full text link
    This chapter reviews the challenges and requirements in taking gaze-based interaction beyond communication and control, such as environmental control and mobility by gaze. The chapter is divided into two sections: the first section is devoted to environment control and the second to mobility control. Each section starts by introducing its necessary underlying notions and definitions and proceeds by explaining the main arguments for the development of environmental and mobility control and examining the general problems with these areas and of those domain-specific problems related to gaze control. While special attention is devoted to standardization when environment control is at issue, user safety is the priority in mobility control. A brief review of existing commercial or advanced research solutions offered for domotic and mobility control is given for both sections, as is a review of current open research issues. Finally, some promising academic prototypes are described, along with the ways in which their developers are trying to solve some of the problems identifie

    Structure of Iron Oxide Nanoparticles Studied by 57Fe\text{}^{57}Fe NMR

    Full text link
    In this work we apply nuclear magnetic resonance (NMR) spectroscopy of 57Fe\text{}^{57}Fe nuclei for investigation of submicron and nanocrystalline iron oxide systems. The studied iron oxide particles are obtained from ferrous hydroxide gels (prepared from FeCl2FeCl_{2} and KOH) by aging at elevated temperatures (90 °C) with KNO3KNO_{3} as oxidant. The 57Fe\text{}^{57}Fe NMR spectra of the samples are measured in temperature range 4.2-370 K in a zero external magnetic field. Signals of 57Fe\text{}^{57}Fe nuclei assigned to tetrahedral and octahedral iron sites are well resolved. The NMR spectra and their temperature dependences are compared with those of stoichiometric and nonstoichiometric magnetite single crystals, as well as with samples of maghemite

    NMR Study of Multiferroic Iron Niobate Perovskites

    Full text link
    We present 93Nb\text{}^{93}Nb, 207Pb\text{}^{207}Pb and 135,137Ba\text{}^{135,137}Ba NMR study of multiferroic lead iron niobate and barium iron niobate ceramics. We ascribe development of NMR spectra on cooling below room temperature to magnetism of ferric ions close to resonating nuclei and introduce a framework capable of describing key features of the observed temperature induced changes. We show that the ferric ions have much stronger influence on hyperfine fields at nuclei of large cations in lead compound and estimate strength of interaction of superantiferromagnetic clusters

    Antisite Defects in Epitaxial Films of Lutetium Doped Yttrium Iron Garnets Studied by Nuclear Magnetic Resonance

    Full text link
    Series of lutetium doped yttrium iron garnet films is studied by means of 57Fe\text{}^{57}Fe nuclear magnetic resonance. Satellite spectral lines are resolved and identified in the spectra and concentrations of lutetium in dodecahedral sites as well as yttrium/lutetium antisite defects in octahedral sites are estimated. Compared to yttrium, lutetium cations are found to have stronger disposition towards creating the antisite defects
    corecore