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162 results on '"Kareev, M."'

151. Evolution of ferromagnetism in two-dimensional electron gas of LaTiO3/SrTiO3.

Author

Wen, Fangdi, Cao, Yanwei, Liu, Xiaoran, Pal, B., Middey, S., Kareev, M., and Chakhalian, J.

Subjects
FERROMAGNETISM, ELECTRONS, LEPTONS (Nuclear physics), TEMPERATURE, PHOTOELECTRON spectroscopy
Abstract

Understanding, creating, and manipulating spin polarization of two-dimensional electron gases at complex oxide interfaces present an experimental challenge. For example, despite almost a decade long research effort, the microscopic origin of ferromagnetism in LaAlO3/SrTiO3 heterojunctions is still an open question. Here, by using a prototypical two-dimensional electron gas (2DEG) which emerges at the interface between band insulator SrTiO3 and antiferromagnetic Mott insulator LaTiO3, the experiment reveals the evidence for magnetic phase separation in a hole-doped Ti d1 t2g system, resulting in spin-polarized 2DEG. The details of electronic and magnetic properties of the 2DEG were investigated by temperature-dependent d.c. transport, angle-dependent X-ray photoemission spectroscopy, and temperature-dependent magnetoresistance. The observation of clear hysteresis in magnetotransport at low magnetic fields implies spin-polarization from magnetic islands in the hole rich LaTiO3 near the interface. These findings emphasize the role of magnetic instabilities in doped Mott insulators, thus providing another path for designing all-oxide structures relevant to spintronic applications. [ABSTRACT FROM AUTHOR]

Published
2018
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154. Charge order and antiferromagnetism in epitaxial ultrathin films of EuNiO3.

Author

Meyers, D., Middey, S., Kareev, M., Liu, Jian, Kim, J. W., Shafer, P., Ryan, P. J., and Chakhalian, J.

Subjects
*NICKEL oxides, *ANTIFERROMAGNETISM, *METALLIC thin films, *DIMENSION reduction (Statistics), *ANTIFERROMAGNETIC materials, *X-ray scattering
Abstract

On a road towards applications and devices based on functional oxides with correlated electrons, the crucial element is uncovering the effects of the reduced dimensionality on the electronic phase transition into a multiordered ground state. Towards this goal, we present a study of reduced dimensionality on charge and antiferromagnetic orderings in ultrathin EuNiO3 films on NdGaO3 substrates using hard and soft resonant x-ray scattering to investigate the presence of electronic and magnetic orderings. Despite the ultrathin nature of the films, they exhibit the bulklike order parameters up to room temperature, suggesting that the spontaneously coherent Mott ground state in the highly distorted rare-earth nickelates can be successfully sustained even when constrained towards two-dimensionality. The presence of charge ordering at room temperature and below opens prospects for their use in novel electric-field-controlled devices. [ABSTRACT FROM AUTHOR]

Published
2015
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155. Orbital configuration in CaTiO3 films on NdGaO3.

Author

Yanwei Cao, Park, Se Young, Xiaoran Liu, Choudhury, D., Middey, S., Meyers, D., Kareev, M., Shafer, P., Arenholz, E., and Chakhalian, J.

Subjects
*ELECTRODE reactions, *ELECTRONIC structure, *PULSED laser deposition, *X-ray absorption, *LINEAR dichroism
Abstract

Despite its use as a constituent layer for realization of a polar metal and interfacial conductivity, the microscopic study of electronic structure of CaTiO3 is still very limited. Here, we epitaxially stabilized CaTiO3 films on NdGaO3 (110) substrates in a layer-by-layer way by pulsed laser deposition. The structural and electronic properties of the films were characterized by reflection high-energy-electron-diffraction, X-ray diffraction, and element-specific resonant X-ray absorption spectroscopy. To reveal the orbital polarization and the crystal field splitting of the titanium 3d state, X-ray linear dichroism was carried out on CaTiO3 films, demonstrating the orbital configuration of dxz/dyz

Published
2016
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157. Optical study of strained ultrathin films of strongly correlated LaNiO3.

Author

Stewart, M. K., Yee, C.-H., Jian Liu, Kareev, M., Smith, R. K., Chapler, B. C., Varela, M., Ryan, P. J., Haule, K., Chakhalian, J., and Basov, D. N.

Subjects
*PHYSICS research, *THIN films, *TENSILE architecture, *COATING processes, *TEMPERATURE, *THERMAL conductivity
Abstract

An optical study of fully strained ultrathin LaNiO3 films is presented and compared with LDA?+?DMFT calculations. LaNiO3 films were grown by pulsed laser deposition on LaAlO3 and SrTiO3 substrates which provide compressive and tensile strain, respectively. Optical conductivity data show a Drude peak with a spectral weight that is significantly reduced compared to that obtained from LDA calculations. The extended Drude analysis reveals the presence of a pseudogap around 80 meV for the film on SrTiO3 and near 40 meV, at low temperature only, for the film on LAO. An unusual temperature dependence of the optical conductivity is observed, with the Drude plasma frequency increasing by up to 20% at low temperature due to spectral weight transfer from bands lying 2-4 eV below the Fermi energy. Such a strong temperature dependence of the Drude spectral weight has previously been reported for correlated electron systems in which a phase transition is present. In LaNiO3, however, no phase transition is observed. [ABSTRACT FROM AUTHOR]

Published
2011
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158. Philosophical ideas and principles in historical cognition

Author

Sinyakov Sergey Vasilievich

Subjects
social history, value, philosophy, historical perception, ideology, methodology, conception, paradigm, historical science, concept, positivism
Abstract

The mechanisms of interrelation between ideological values and methodological means of historical perception are revealed in the article. The role of philosophy as a theoretical centre of the ideology is underlined in the article. The participation of philosophical ideas in the formation of historical conceptions and categorical mechanisms of historical science, in the evolution of historical concepts, in the development of the methods of the perception of the past and the subject field of the research is discussed in the article. The categorical apparatus of historical science is an instrument for the production of new knowledge, an instrument of the theoretical consciousness of а historian. Therefore, the development and change of historical knowledge systems causes a consequence of changes in categorical structures, each of which associates its semantic field of historical explanations with its composition and method of questioning. The categorical system of thinking in historical science is a synthesis of philosophical, sociological, psychological, culturological and historical concepts. Historical concepts, as the result of the development of both historical and socio-humanitarian knowledge, at the same time serve as the main tool of cognition of the past. The nature of historical concepts is determined, on the one hand, by the peculiarities of the subject area of historical cognition, on the other hand, by the system of categories of philosophy and other social sciences. The source of the content of historical concepts is the past itself as an object of knowledge, and the whole set of theoretical means of modern social cognition. Permeating all historical cognition, the concepts of philosophy and culture act as deep programs of research, which provide a connection of historical facts, their explanation with philosophical and ideological concepts of the modern era. The methodology of historical cognition is always summarized in a certain set of concepts on the basis of philosophical premises. The history of historical science shows that no one new philosophical methodology has been left without the attention of historians. The role of philosophical ideas and principles, their impact on the methodology of history can be seen in the best way during changes of ideological foundations of historical knowledge. The article considers the revision of methods of historical research in Russian historiography at the turn of the 19th and 20th centuries, in the works of N. I. Kareev, M. M. Kovalevsky, R. Yu. Wipper, A. S. LappoDanilevsky, the transition from positivist philosophical principles and cognitive means to neo-Kantian methods in specific historical research, attempts of psychological interpretation of historical events. The philosophical significance of philosophy is revealed in the discussion on such problems of historical epistemology as the problem of reliability of historical knowledge, the issue of historical truth, the nature and content of historical concepts. Philosophy is an important means of stating and solving ontological problems of history: the place of the man in the historical process, his freedom, the meaning and purpose of history, the sources and driving forces of historical development. The authors underline the specific features of historical perception, the importance of micro-ideas which show the unique nature of social phenomena of the past for it. The change in the system of concepts of historical science in connection with the change of philosophical conceptions as well as historical approaches (social history, “Annals” school, new social history) is shown in the article.

Published
2020
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159. К истокам компетентностного подхода (либеральные историки конца XIX – начала XX вв. О реформе образования в России)

Subjects
Д.М.ПЕТРУШЕВСКИЙ, D. M. PETRUSHEVSKY, П.Н.МИЛЮКОВ, А. С. ЛАППО-ДАНИЛЕВСКИЙ, A. S. LAPPO-DANILEVSKY, М.М.КОВАЛЕВСКИЙ, M. M. KOVALEVSKY, Н.И.КАРЕЕВ, П.Г.ВИНОГРАДОВ, P.G. VINOGRADOV, ИСТОРИЧЕСКОЕ ЗНАНИЕ, РЕФОРМЫ ОБРАЗОВАНИЯ, КОМПЕТЕНТНОСТНЫЙ ПОДХОД, ЛИБЕРАЛЬНАЯ ИСТОРИОГРАФИЯ, P. N. MILYUKOV, N. I. KAREEV
Abstract

Проблема реформирования образования проанализирована автором как интегральная социальная категория. Научное исследование подходов и методологии проводимых преобразований в сфере высшего образования проведено в контексте рассмотрения оригинальных исторических источников. Новизна исследования обусловлена методологией историко-сравнительного сопоставления наследия российской либеральной историографии конца XIX – начала XX вв. с современными проектами преобразований системы образования. Широкий спектр архивных материалов, введенный в научный оборот, конкретизирует теоретические положения статьи. Источниковую базу исследования составили фонды таких отечественных архивов, как: АРАН (Архив Российской Академии наук (Москва), ГАРФ (Государственный архив Российской Федерации (Москва), ОР РГБ (Отдел рукописей Российской государственной библиотеки (Москва), ЦИАМ (Центральный исторический архив г. Москвы (Мосгорархив), ПФА РАН (Петербургский филиал Архива Российской Академии наук), РГИА (Российский государственный исторический архив (Санкт-Петербург); отечественные и зарубежные периодические издания. Современная трактовка компетентностного подхода, как метода моделирования образа совершенного специалиста, проанализирована в историографической ретроспективе. Подробный анализ научных концепций и опыта их воплощения П. Г. Виноградовым, Н. И. Кареевым, М. М. Ковалевским, А. С. Лаппо-Данилевским, П.Н.Милюковым, Д. М. Петрушевским, позволил не только подтвердить положение об определяющей роли названных ученых в развитии исторической науки России в конце XIX – начале XX вв., но и сделать вывод о значимости их научно-теоретического и практического опыта в сфере реформирования системы образования., The problem of educational reform has analyzed by the author as an integral social category. Scientific research approaches and methodology of the current reforms in higher education conducted in the context of original historical sources. The scientific novelty of the research due to the methodology of historical-comparative mapping heritage of the Russian liberal historiography of the late XIX early XXth centuries with modern projects of transformation of the education system. A wide range of archival materials introduced into scientific circulation, elaborates on the theoretical framework of the article. The article has based on the holdings of such national archives: ARAN (archive of the Russian Academy of Sciences (Moscow), GARF (State archive of the Russian Federation (Moscow), PR RGB (Department of manuscripts of the Russian state library (Moscow), CIAM (Central historical archive of Moscow (mosgorarhiv), the APF RAS (St. Petersburg branch of the Archive of the Russian Academy of Sciences), RGIA (Russian state historical archive in St. Petersburg); domestic and foreign periodicals. A modern interpretation of the competence-based approach as a method of modeling the image of the perfect specialist, analyzed in historical retrospect. The author has analysed the scientific concepts and experience of their implementation by P.G. Vinogradov, N. I. Kareev, M. M. Kovalevsky, P.N. Milyukov, A. S. Lappo-Danilevsky, D. M. Petrusevski. It has allowed not only to confirm position about the decisive role of scientists named in the development of historical science in Russia in the late XIX early XXth centuries, but also has made a conclusion about the importance of their scientific-theoretical and practical experience in reforming the education system.

Published
2014

160. Evolution of ferromagnetism in two-dimensional electron gas of LaTiO3/SrTiO3.

Author

Wen, Fangdi, Cao, Yanwei, Liu, Xiaoran, Pal, B., Middey, S., Kareev, M., and Chakhalian, J.

Subjects
*FERROMAGNETISM, *ELECTRONS, *LEPTONS (Nuclear physics), *TEMPERATURE, *PHOTOELECTRON spectroscopy
Abstract

Understanding, creating, and manipulating spin polarization of two-dimensional electron gases at complex oxide interfaces present an experimental challenge. For example, despite almost a decade long research effort, the microscopic origin of ferromagnetism in LaAlO3/SrTiO3 heterojunctions is still an open question. Here, by using a prototypical two-dimensional electron gas (2DEG) which emerges at the interface between band insulator SrTiO3 and antiferromagnetic Mott insulator LaTiO3, the experiment reveals the evidence for magnetic phase separation in a hole-doped Ti d1 t2g system, resulting in spin-polarized 2DEG. The details of electronic and magnetic properties of the 2DEG were investigated by temperature-dependent d.c. transport, angle-dependent X-ray photoemission spectroscopy, and temperature-dependent magnetoresistance. The observation of clear hysteresis in magnetotransport at low magnetic fields implies spin-polarization from magnetic islands in the hole rich LaTiO3 near the interface. These findings emphasize the role of magnetic instabilities in doped Mott insulators, thus providing another path for designing all-oxide structures relevant to spintronic applications. [ABSTRACT FROM AUTHOR]

Published
2018
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161. Phase coexistence and dynamical behavior in NdNiO3 ultrathin films.

Author

Alsaqqa, Ali M., Singh, Sujay, Middey, S., Kareev, M., Chakhalian, J., and Sambandamurthy, G.

Subjects
*PHASE transitions, *NICKEL oxide
Abstract

Rare-earth nickelates exhibit several temperature-driven phase transitions that are tunable by the size of the rare-earth ions, pressure, epitaxial strain in ultrathin films, etc. We investigate the metal-insulator and Neel transitions in a series of NdNiO3 thin films with varying degrees of lattice mismatch using ultralow frequency electrical noise measurements. The noise magnitude follows a 1/f behavior and is Gaussian in the high temperature paramagnetic metallic phase of the films, however deviations are seen in the low temperature paramagnetic and antiferromagnetic insulating phases. The noise magnitude increases by orders of magnitude at temperatures below the metal-insulator transition and is indicative of inhomogeneous electrical conduction arising from phase separation. The inhomogeneous nature of conduction is corroborated by the presence of a large non-Gaussian noise signature in the low temperature phases. Well below the Neel temperature, the noise behavior evolves between Gaussian and non-Gaussian over several hours pointing to dynamically competing ground states with subtle variations within the antiferromagnetic insulating phase. [ABSTRACT FROM AUTHOR]

Published
2017
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