Ferrodistorsive orbital ordering in the layered nickelate NaNiO_2: A density-functional study

The electronic structure and magnetism in the sodium nickelate NaNiO_2 in the low-temperature phase is studied from density-functional calculations using the linear muffin-tin orbitals method. An antiferromagnetic solution with a magnetic moment of 0.7 m_B per Ni ion is found. A ferrodistorsive orbital ordering is shown to occur due to the Jahn-Teller distortion around the Ni^{3+} ion in agreement with the orbital ordering inferred from neutron diffraction. While the intralayer exchange is ferromagnetic, the interlayer exchange is weakly antiferromagnetic, mediated by a long Ni-O-Na-O-Ni superexchange path.Comment: 4 pages, 5 figures Submitted to MMM2004 conference Proceeding

Simulation of reconstructions of the polar ZnO (0001) surfaces

Surface reconstructions on the polar ZnO(0001) surface are investigated using empirical potential models. Several possible reconstructions based around triangular motifs are investigated. The quenching of the dipole moment in the material dominates the energetics of the surface patterns so that no one particular size of surface triangular island or pit is strongly favoured. We employ Monte Carlo simulations to explore which patterns emerge from a high temperature quench and during deposition of additional ZnO monolayers. The simulations show that a range of triangular islands and pits evolve in competition with one another. The surface patterns we discover are qualitatively similar to those observed experimentally

Theory of lattice effects on magnetic interactions in solids

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file viewed on (November 13, 2006)Includes bibliographical references.Vita.Thesis (Ph. D.) University of Missouri-Columbia 2005.Dissertations, Academic -- University of Missouri--Columbia -- Physics.This dissertation focuses on studying the effect of lattice distortions on the magnetic properties of nickelates and manganites. These two families of materials have great potential in industrial applications in the fields of magnetic (superdense hard-drives, fast memory) and charge storage (batteries). The introduction and methods sections present the main ideas of the dissertation and discuss the various techniques used. Electron-lattice coupling is first examined in chapter three for a two-site model where we estimate the magnitude of the isotope effect on the critical temperature and show that it decreases magnetic exchange. In the next part we study electronic structure and magnetism of NaNiO2 and show that inter-planar exchange is reduced by lattice coupling. In the fifth chapter we examine the magnetic polaron and discuss the effect of static lattice coupling on its binding energy, and find it to further stabilize the polaron

Elliptic inequalities with lower order terms and L1 data in Orlicz spaces

AbstractWe prove an existence result for solutions of nonlinear elliptic unilateral problems having natural growth terms and L1 data in Orlicz–Sobolev spaces

Exploratory study of Islamic Social Finance in Morocco

Islamic Moral Economy emerged in the late 1960s aiming for the Islamic financial ecosystem to finance the real economy. Practical experiences exhibited double-digit growth of the financial performances of Islamic banking and financial institutions. However, the social purpose of these institutions was lacking. Indeed, one of the biggest critics of the modern Islamic Finance industry are its weaknesses in terms of social performances. Many researchers mourn the lack of an effective institutionalization of the Islamic principles mentioned in religious sources that could alleviate poverty; such as Zakat, Waqf and Qard Al Hassan. Institutionalized Islamic social models are deployed and presented as solutions to overcome the issue. As for that, several initiatives have been developed all around the Islamic world, using local and governmental initiatives alongside with other Islamic-based actions; in order to alleviate poverty and unemployment, and to encourage investments and entrepreneurship of a targeted population’s financial inclusion. In Morocco, although social Islamic finance does not exist under this denomination; several initiatives launched by the governmental institutions, the civil society and sometimes even by individual and informal actions are taking place. Most of these are backed by Islamic principles as it has been religiously, historically and culturally inherited in the Moroccan society

Jahn-Teller coupling and double exchange in the two-site Van Vleck-Kanamori model

http://link.aip.org/link/JAPIAU/v85/i8/p4346/s1 doi:10.1063/1.369780The effect of the dynamical Jahn-Teller coupling on the Anderson-Hasegawa double exchange (DE) in the manganites is studied in a two-site model taking into account the double degeneracy of the eg orbitals and their coupling to the three MnO6 vibrational modes (Q1 , Q2 , and Q3). Both exact diagonalization and the Lang-Firsov approach are used. We find that coupling to the Q2 and Q3 modes reduces the DE, while the Q1 mode is ineffective. The isotope dependence of the DE interaction is consistent with recent experiments.The authors thank the Research Board of the University of Missouri for partial financial support

Orbital ordering and exchange interaction in the manganites

URL:http://link.aps.org/doi/10.1103/PhysRevB.64.094433 DOI:10.1103/PhysRevB.64.094433The microscopic origin of the exchange interaction in manganites is studied by solving an electronic model Hamiltonian for the Mn-O-Mn triad. It is shown that the magnetic structure of La1-xCaxMnO3 is correctly described within an electronic Hamiltonian model, provided that the appropriate orientation of the Mn(eg) orbitals induced by the Jahn-Teller effect is taken into account. The Jahn-Teller distortions of the MnO6 octahedra control the orientation of the eg orbitals in the crystal, which in turn is shown to determine the sign of the magnetic exchange. Electron hopping involving the Mn(t2g) orbitals is found to be important in certain situations, for instance, it can cause a sign change in the exchange interaction, from ferromagnetic to antiferromagnetic, as a function of the Mn-O-Mn bond angle. All our results are obtained by exact diagonalization of the model Hamiltonian, either by direct diagonalization or by diagonalization using the Lanczos method, if the Hamiltonian is too big, and are rationalized using results of the fourth-order perturbation theory. The exchange interactions (signs and magnitudes) of the end members LaMnO3 and CaMnO3 as well as of the half-doped compound, La1/2Ca1/2MnO3, are all described correctly within the model.This work was supported in part by a grant from the Department of Energy under Contract No. DOE FG02-00E0045818

Erratum: Orbital ordering and exchange interaction in the manganites [Phys. Rev. B 64, 094433 (2001)]

Refers to: http://hdl.handle.net/10355/9317 URL:http://link.aps.org/doi/10.1103/PhysRevB.68.029901 DOI:10.1103/PhysRevB.68.029901Erratum concerning Orbital ordering and exchange interaction in the manganites [Phys. Rev. B 64, 094433 (2001)]

Dinamización del talento del territorio valenciano mediante unas Jornadas de Música Emergente dentro del ámbito universitario

[ES] El presente Trabajo de Fin de Máster es un programa piloto, un primer ejercicio, que desea asentar unas nuevas bases y formas de hacer en la cultura dentro del ámbito universitario. Este trabajo pretende ayudar al desarrollo cultural y social a futuro mediante la creación de unas jornadas musicales que funcionen como agente dinamizador de la cultura dentro de las propias universidades, espacios que deben ser impulsores del talento emergente. Consideramos que los horizontes de la universidad han de ser capaces de ayudar a la producción de bienes y servicios culturales, funcionando estos, como un vector de desarrollo social para el progreso colectivo. En estos tiempos de crisis, la cultura ha sido la arquitectura de supervivencia como sujetos sociales. Estas incertidumbres generales derivadas de la pandemia a nivel global provocada por el COVID-19, solo se pueden hacer frente con una mayor consciencia compartida de los retos y potenciales comunes que tenemos como productores de cultura. La crisis impuesta al sector cultural debe ser resuelta. Esto implica la necesidad de combatir los nuevos paradigmas, que han cambiado de forma forzosa y en un tiempo récord, las formas de hacer proyectos o eventos culturales a las que estábamos acostumbrados. Con la llegada de la definida como "nueva normalidad", se pretende crear un proyecto que puede funcionar a futuro y que se adapte a estas nuevas realidades. Es por ello, por lo que nos vemos en la necesidad de generar un nuevo protocolo de intervención cultural, que pueda desarrollarse en los campus de las universidades del territorio valenciano, ayudando a su progreso.Creemos que la música es un elemento clave en tiempo convulsos, y así se ha demostrado durante este tiempo de cuarentena en 2020. Por otro lado, gracias a las tecnologías nos hemos sentido conectados, y estas han servido de puente de difusión y esperanza del bienestar cultural. Pero, por otro lado, estas mismas tecnologías, han hecho que echemos más que nunca de menos el vivir y sentir en directo las voces y las vibraciones de los intérpretes y sus instrumentos musicales. Por lo tanto, nuestra misión en este proyecto es la de mediante la creación de un micro-festival o jornadas musicales, potenciar el talento y, asimismo, volver a conectar a la gente con la cultura en vivo de forma segura, reforzado la idea de que las universidades son los espacios idóneos para el desarrollo y buena articulación de estas dinámicas culturales por medio de la música.[EN] This Master's Thesis is a pilot program, a first exercise, which aims to establish new foundations and ways of doing culture within the university environment. This work aims to help future cultural and social development through the creation of musical sessions that function as a catalyst for culture within the universities themselves, spaces that should be drivers of emerging talent. We consider that the horizons of the University must be capable of helping the production of cultural goods and services, functioning as a vector of social development for collective progress. In these times of crisis, culture has been the architecture of survival as social subjects. These general uncertainties derived from the global pandemic caused by COVID-19 can only be addressed with a greater shared awareness of the common challenges and potentials that we have as producers of culture. The crisis imposed on the cultural sector must be resolved. This implies the need to combat the new paradigms, which have forcibly changed and in record time, the ways of doing cultural projects or events to which we were accustomed. With the arrival of what is defined as the "new normal", it is intended to create a project that can work in the future and that adapts to these new realities. That is why we see ourselves in the need to generate a new protocol of cultural intervention, which can be developed on the campuses of the universities of the Valencian territory, helping their progress. We believe that music is a key element in troubled times , and this has been demonstrated during this time of quarantine in 2020. On the other hand, thanks to technologies we have felt connected, and these have served as a bridge of diffusion and hope for cultural well-being. But, on the other hand, these same technologies have made us miss more than ever living and feeling the voices and vibrations of the performers and their musical instruments live. Therefore, our mission in this project is to promote talent and, by creating a micro-festival or musical days, to reconnect people with live culture in a safe way, reinforcing the idea of that universities are the ideal spaces for the development and good articulation of these cultural dynamics through music.Meskine Gumbau, F. (2021). Dinamización del talento del territorio valenciano mediante unas Jornadas de Música Emergente dentro del ámbito universitario. Universitat Politècnica de València. http://hdl.handle.net/10251/173260TFG