Cobalt nanoparticles on the surface of highly oriented pyrolytic graphite have been studied by atomic force microscopy. Thermal annealing in ultrahigh vacuum was used to change the size of cobalt nanoparticles and the...Cobalt nanoparticles on the surface of highly oriented pyrolytic graphite have been studied by atomic force microscopy. Thermal annealing in ultrahigh vacuum was used to change the size of cobalt nanoparticles and their surface distribution. The effect of two key parameters, annealing time and temperature, on the size and the surface distribution of nanoparticles has been studied. The dependence of the particle size on these parameters has been obtained. It has been shown that the main mechanism of the nanoparticle growth is Ostwald ripening.展开更多
Superconducting spin valves based on the superconductor/ferromagnet （S/F） proximity effect are considered to be a key element in the emerging field of superconducting spintronics. Here, we demonstrate the crucial ro...Superconducting spin valves based on the superconductor/ferromagnet （S/F） proximity effect are considered to be a key element in the emerging field of superconducting spintronics. Here, we demonstrate the crucial role of the morphology of the superconducting layer in the operation of a multilayer S/F1/F2 spin valve. We study two types of superconducting spin valve heterostructures, with rough and with smooth superconducting layers, using transmission electron microscopy in combination with transport and magnetic characterization. We find that the quality of the S/F interface is not critical for the S/F proximity effect, as regards the suppression of the critical temperature of the S layer. However, it appears to be of paramount importance in the performance of the S/F1/F2 spin valve. As the morphology of the S layer changes from the form of overlapping islands to a smooth case, the magnitude of the conventional superconducting spin valve effect significantly increases. We attribute this dramatic effect to a homogenization of the Green function of the superconducting condensate over the S/F interface in the S/F1/F2 valve with a smooth surface of the S laver.展开更多
Thin epitaxial films of the palladium-rich Pd_(1-x)Fe_(x) alloy were synthesized and extensively studied as a tunable ferromagnetic material for superconducting spintronics. The(001)-oriented Mg O single-crystal subst...Thin epitaxial films of the palladium-rich Pd_(1-x)Fe_(x) alloy were synthesized and extensively studied as a tunable ferromagnetic material for superconducting spintronics. The(001)-oriented Mg O single-crystal substrate and the composition range of x = 0.01–0.07 were chosen to support the epitaxial growth and provide the films with magnetic properties spanning from very soft ferromagnet for memory applications to intermediately soft and moderately hard for the programmable logic and circuit biasing, respectively. Dependences of the saturation magnetization, Curie temperature and three magnetic anisotropy constants on the iron content x were obtained for the first time from the analyses of the magnetometry and ferromagnetic resonance data. The experimental results were discussed based on existing theories of dilute ferromagnetic alloys. Simulation of the hysteresis loops within the Stoner-Wohlfarth model indicates the predominant coherent magnetic moment rotation at cryogenic temperatures. The obtained results were compiled in a database of magnetic properties of a palladium-iron alloy in a single-crystal thin-film form considered as a material for superconducting spintronics.展开更多
The objects of the investigation were uniformly Ag~＋ doped Hg_（0.76）Cd_（0.24） Te mercury chalcogenide monocrystals obtained by ion implantation with subsequent thermal annealing over 20 days. After implantation a...The objects of the investigation were uniformly Ag~＋ doped Hg_（0.76）Cd_（0.24） Te mercury chalcogenide monocrystals obtained by ion implantation with subsequent thermal annealing over 20 days. After implantation and annealing the conductivity was inverted from n-type with carrier concentration of 10^（16） cm^（-3） to p-type with carrier concentration of ≈ 3.9 × 10^（15） cm^（-3）. The investigations of microwave absorption derivative（d P/d H） showed the existence of strong oscillations in the magnetic field for Ag：Hg_（0.76）Cd_（0.24） Te in the temperature range 4.2–12 K. The concentration and effective mass of charge carrier were determined from oscillation period and temperature dependency of oscillation amplitude. We suppose that this phenomenon is similar to the de Haas–van Alphen effect in weakly correlated electron system with imperfect nesting vector.展开更多
文摘Cobalt nanoparticles on the surface of highly oriented pyrolytic graphite have been studied by atomic force microscopy. Thermal annealing in ultrahigh vacuum was used to change the size of cobalt nanoparticles and their surface distribution. The effect of two key parameters, annealing time and temperature, on the size and the surface distribution of nanoparticles has been studied. The dependence of the particle size on these parameters has been obtained. It has been shown that the main mechanism of the nanoparticle growth is Ostwald ripening.
文摘Superconducting spin valves based on the superconductor/ferromagnet （S/F） proximity effect are considered to be a key element in the emerging field of superconducting spintronics. Here, we demonstrate the crucial role of the morphology of the superconducting layer in the operation of a multilayer S/F1/F2 spin valve. We study two types of superconducting spin valve heterostructures, with rough and with smooth superconducting layers, using transmission electron microscopy in combination with transport and magnetic characterization. We find that the quality of the S/F interface is not critical for the S/F proximity effect, as regards the suppression of the critical temperature of the S layer. However, it appears to be of paramount importance in the performance of the S/F1/F2 spin valve. As the morphology of the S layer changes from the form of overlapping islands to a smooth case, the magnitude of the conventional superconducting spin valve effect significantly increases. We attribute this dramatic effect to a homogenization of the Green function of the superconducting condensate over the S/F interface in the S/F1/F2 valve with a smooth surface of the S laver.
文摘Thin epitaxial films of the palladium-rich Pd_(1-x)Fe_(x) alloy were synthesized and extensively studied as a tunable ferromagnetic material for superconducting spintronics. The(001)-oriented Mg O single-crystal substrate and the composition range of x = 0.01–0.07 were chosen to support the epitaxial growth and provide the films with magnetic properties spanning from very soft ferromagnet for memory applications to intermediately soft and moderately hard for the programmable logic and circuit biasing, respectively. Dependences of the saturation magnetization, Curie temperature and three magnetic anisotropy constants on the iron content x were obtained for the first time from the analyses of the magnetometry and ferromagnetic resonance data. The experimental results were discussed based on existing theories of dilute ferromagnetic alloys. Simulation of the hysteresis loops within the Stoner-Wohlfarth model indicates the predominant coherent magnetic moment rotation at cryogenic temperatures. The obtained results were compiled in a database of magnetic properties of a palladium-iron alloy in a single-crystal thin-film form considered as a material for superconducting spintronics.
文摘The objects of the investigation were uniformly Ag~＋ doped Hg_（0.76）Cd_（0.24） Te mercury chalcogenide monocrystals obtained by ion implantation with subsequent thermal annealing over 20 days. After implantation and annealing the conductivity was inverted from n-type with carrier concentration of 10^（16） cm^（-3） to p-type with carrier concentration of ≈ 3.9 × 10^（15） cm^（-3）. The investigations of microwave absorption derivative（d P/d H） showed the existence of strong oscillations in the magnetic field for Ag：Hg_（0.76）Cd_（0.24） Te in the temperature range 4.2–12 K. The concentration and effective mass of charge carrier were determined from oscillation period and temperature dependency of oscillation amplitude. We suppose that this phenomenon is similar to the de Haas–van Alphen effect in weakly correlated electron system with imperfect nesting vector.
