Sinusoidal electromagnon in RMnO3: Indication of anomalous magnetoelectric coupling

The optical spectra in the family of multiferroic manganites RMnO3 is a great puzzle. Current models can not explain the fact that two strong electromagnons are present in the non-collinear spin cycloidal phase, with only one electromagnon surviving the transition into the collinear spin sinusoidal phase. We show that this is a signature of the presence of anomalous magnetoelectric coupling that breaks rotational invariance in spin space and generates oscillatory polarization in the ground state.Comment: 5 pages, 2 figure

Plano de gestão para a Embrapa Meio-Norte.

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Expansive and collapsing behaviour of volume change soils

This thesis is designed to achieve three goals: Goal One - to introduce the reader to soils exhibiting expansive and/or collapsing behaviour; Goal Two - to provide an in depth understanding of aspects of this behaviour, obtained from an extensive study of these soil types; and, Goal Three - to serve as a reference for future research work (a recommendation for further research proposed in Chapter Ten of this thesis). The thesis is divided in two main parts. In the first part representative soil types were selected on the basis of their properties and expected engineering behaviour. The soil structure and clay minerals were also studied in part one of this thesis. The second part of the thesis deals with aspects of expansive and collapsing behaviour of soils. Chapter three provides the introduction to the subsequent chapters on expansive and collapsing behaviour of volume change soils

A simple deterministic self-organized critical system

We introduce a new continuous cellular automaton that presents self-organized criticality. It is one-dimensional, totally deterministic, without any kind of embedded randomness, not even in the initial conditions. This system is in the same universality class as the Oslo rice pile system, boundary driven interface depinning and the train model for earthquakes. Although the system is chaotic, in the thermodynamic limit chaos occurs only in a microscopic level.Comment: System slightly modified. New results on Liapunov exponents. Submitted for publication (8 pages

Alterações nas características químicas de um latossolo amarelo sob sistemas agroflorestais com cupuaçuzeiro no município de Presidente Figueiredo, AM.

Avaliação de algumas características químicas de um latossolo amarelo distrófico, sob dois sistemas agroflorestais com três tipos de manejo de adubação, durante oito anos