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For years graphene has been considered as the most potential material which paves the way to advanced high-performance spintronic devices due to its extraordinary electrical and physical properties. The long spin diffusion length in graphene originated from the weak spin-orbit interaction and high electron mobility has stimulated numerous studies on developing graphene-based lateral spin valves (SV) in the past decade [1]. Apart from the application to lateral SV dealing with in-plane spin transportation in a graphene channel, another potential application that is the implementation of graphene as a spacer material in vertical SV has become a subject of intense interest in recent years [2]. In those reported graphene-spintronic devices, conventional ferromagnets such as NiFe and Co etc. of low spin polarization have been used due to the well-established synthesis method of graphene on them. However, the low spin signal and tiny magnetoresistance effect reported in those systems make graphene still far from being considered satisfactory for spintronic device applications. Adopting highly spin-polarized material such as half-metals can be the most effective way to improve the performance of graphene spintronic devices, the experimental demonstration, however, is still lacking. Here, we report the demonstration of the in-situ fabrication of a novel heterostructure consisting of graphene and full Heusler alloy Co2Fe(Ge0.5Ga0.5) (CFGG), in which half-metallicity has been confirmed experimentally [3]. Single layer graphene was prepared by in situ chemical vapor deposition on a magnetron sputtered epitaxial CFGG thin film grown on single crystalline MgO(001) substrate. As shown by the RHEED images in Fig. 1, the sharp streaky patterns from both graphene and CFGG indicate an atomic flatness of the SLG/CFGG interface. The high quality of graphene was further confirmed by Raman spectroscopy. A depth-resolved XMCD study reveals that the CFGG surface adjacent to SLG possesses a robust magnetic moment comparable to the bulk CFGG (Fig. 2) in association with the weak interfacial interaction between graphene on CFGG. This finding is in sharp contrast to the large reduction of the magnetic moment reported in other graphene/ferromagnets heterostructures. DFT calculations show that, the inherent properties such as half-metallicity of CFGG and the linear Dirac band of graphene are preserved at the interface. These findings are highly promising for realizing effective transport of highly spin-polarized electrons in graphene-based spintronic devices [1]W. Han et al, Nat. Nanotechnol. 9, 794 (2014) [2] E. D. Cobas, et al, ACS Nano 10, 10357 (2016) [3] S. Li et al, Appl. Phys. Lett. 103, 042405 (2013), 63th international conference on Magnetism and Magnetic Materials (MMM) 2019に出席するため

As a zero-gap semiconductor with a pin-hole free nature, graphene was proposed as an attractive low energy barrier for vertical spin-valves (SV) to solve the trade-off between MR ratio and low RA product usually observed in MgO-based vertical SV. So far, the MR ratio reported in graphene-spacer vertical SV is far below the application level due to the usage of conventional ferromagnetic electrodes (Ni, Co, Fe etc.) with low spin polarization. Utilizing high spin-polarized ferromagnetic electrodes such as full Heusler alloys is potential way to enhance the MR ratio in graphene-spacer SV, however, there is no precedent for success in the growth of graphene on Heusler alloy underlayer. In this study, we report on the demonstration and characterization of a novel heterostructure consisting of single-layer graphene (SLG) synthesized by high-vacuum chemical vapor deposition (CVD) on a half-metallic Co2Fe(Ge0.5Ga0.5) (CFGG) Heusler alloy, which provides a promising building block for developing high performance graphene-spacer vertical SV., 日本応用物理学会講演会

A novel heterostructure consisting of single-layer graphene (SLG) synthesized by high-vacuum chemical vapor deposition (CVD) on a half-metallic Co2Fe(GeGa) (CFGG) Heusler alloy was demonstrated in this work. In the SLG/CFGG heterostructure, comparing with other SLG/ferromagnet systems, the chemical bonding between SLG and CFGG was found to be rather weak through an x-ray absorption spectra study of SLG near the C K-edge, which indicates a quasi-freestanding nature of the SLG synthesized on CFGG. Depth resolved magnetic circular dichroism (XMCD) measurement suggests there is no degradation on the magnetic property of CFGG at the interface of SLG/CFGG heterostructure, which further confirms the physical nature of the interface between SLG and CFGG. First-principle calculation results show the Dirac cone of SLG and half-metallic band structure of CFGG at the interface are both preserved in the SLG/CFGG heterostructure. Those striking features make the SLG/CFGG heterostructure an extremely promising building block for developing high performance spintronic devices such as magnetic field sensor, magnetic random access memory and spin-transistor., NIMS Week 2018

В статье дан анализ межгосударственных взаимоотношений по вопросам управления водными ресурсами в целях развития четырех стран региона – Казахстана, Кыргызстана, Таджикистана и Узбекистана. Временные рамки исследования охватывают период с начала 1990-х гг. и по настоящее время. Первым шагом в этом направлении стало подписание в 1992 г. соглашения о создании Межгосударственной координационной водохозяйственной комиссии, что знаменует собой начало новой «водной дипломатии» между странами. С тех пор было подписано несколько других документов. Однако не все соглашения были реализованы или одобрены одной или несколькими странами. На сегодняшний день в Центральной Азии существуют основания для развития потенциальных локальных или региональных конфликтов ввиду невыработанных механизмов пользования и предоставления водных ресурсов. В качестве обозначенной проблемы предлагается решение в логике двухуровневого игрового подхода Путнэма. В ходе ведения международных переговоров использование предлагаемых инструментов в рамках теории игр, которые будут оказывать поддержку вовлеченным сторонам с точки зрения количественной оценки и моделирования процессов, является фундаментальным компонентом для предотвращения и разрешения конфликтов., In this article, intergovernmental relations on water resources management and the impact on development between the four countries of the region - Kazakhstan, Kyrgyzstan, Tajikistan and Uzbekistan - will be analyzed. The time frame of the study covers the period of independence in the early 1990s and to the present. The first step in this direction was the signing in 1992 of an agreement on the establishment of an Interstate Commission for Water Coordination. This marks the beginning of a new "water diplomacy" between the countries. Since then, several other documents have been signed and signed. However, not all agreements have been implemented or approved by one or more countries. Today in Central Asia, there are grounds for the development ofpotential local or regional conflicts due to undeveloped mechanisms for the use and provision of water resources. As a designated problem, a solution is proposed in the logic of Putnam's two-tier game approach. In the course of conducting international negotiations, the use of the proposed tools, within the framework of game theory, which will support the parties involved in terms of quantitative assessment and modeling of processes, is a fundamental component for conflict prevention and resolution.

Involving graphene into spin-valve (SV) structures has attracted great attention due to its extraordinary spin transport and essential physical properties useful for advanced spintronic devices. Graphene/ferromagnet heterostructure-based vertical SV is expected to offer large magnetoresistance effect without impairing the electrical conductivity, which enables higher speed and lower power consumption operation of magnetic memory devices. Herein, we report the synthesis and spin-dependent electronic properties of a novel heterostructure which consists of single-layer graphene (SLG) and half-metallic Co2Fe(Ge0.5Ga0.5) (CFGG) Heusler alloy ferromagnet as a promising building block for graphene-based SV. The growth of high quality SLG with complete coverage was demonstrated by ultra-high vacuum chemical vapor deposition on a magnetron-sputtered single crystalline CFGG thin film. A quasi-freestanding nature of SLG and robust magnetism of CFGG at the SLG/CFGG interface was revealed through depth-resolved x-ray magnetic circular dichroism spectroscopy. Density functional theory calculation results indicate that the inherent properties of SLG and CFGG such as the linear Dirac band and half-metallicity are preserved in the vicinity of the interface. These findings indicate the SLG/CFGG heterostructure possesses distinctive advantage over other reported graphene/ferromagnets heterostructures, for realizing effective transport of highly spin-polarized electrons in graphene-based vertical SV and other spintronic devices.