Electric-dipole active two-magnon excitation in {\textit{ab}} spiral spin phase of a ferroelectric magnet Gd0.7_{\textbf{0.7}}Tb0.3_{\textbf{0.3}}MnO3_{\textbf 3}

A broad continuum-like spin excitation (1--10 meV) with a peak structure around 2.4 meV has been observed in the ferroelectric $ab$ spiral spin phase of Gd$_{0.7}$Tb$_{0.3}$MnO$_3$ by using terahertz (THz) time-domain spectroscopy. Based on a complete set of light-polarization measurements, we identify the spin excitation active for the light $E$ vector only along the a-axis, which grows in intensity with lowering temperature even from above the magnetic ordering temperature but disappears upon the transition to the $A$-type antiferromagnetic phase. Such an electric-dipole active spin excitation as observed at THz frequencies can be ascribed to the two-magnon excitation in terms of the unique polarization selection rule in a variety of the magnetically ordered phases.Comment: 11 pages including 3 figure

Local canopy disturbance as an explanation for long‐term increases in liana abundance

Environmental Biolog

JIM - A Java Interagent for Multi-Agent Systems

In this paper we introduce an interagent as an autonomous software agent which manages (intermediates) the communication and coordination between an agent and the agent society wherein this is situated. According to our proposal, interagents shall constitute the sole and exclusive means through which agents within a multi-agent scenario interact. With this aim, we have developed JIM, a general-purpose interagent that provides agents with a highly versatile range of programmable -- before and during the agent's run-time -- communication and coordination services. The development of JIM lies in the framework of the SMASH project. SMASH addresses the construction of multi-agent systems to tackle complex problems of distributed nature in hospital environments. Two main benefits stem from the usage of JIM: on the one hand, it permits agents to reason about both communication and coordination at a higher level of abstraction, whereas on the other hand, it provides a complete set of faciliti..

Electrically active magnetic excitations in antiferromagnets (Review Article)

The magnetic resonance operation by electric field is highly nontrivial but the most demanding function in the future spin-electronics. Recently observed in a variety of multiferroics materials named the collective electrically active magnetic excitations, frequently referred to as “electromagnons”, reveal a possible way to implement such a function. Experimental advances in terahertz spectroscopy of electromagnons in multiferroics as well as related theoretical models are reviewed. The earlier theoretical works, where the existence of electric-dipole active magnetic excitations in antiferro- and ferrimagnets with collinear spin structure has been predicted, are also discussed. Multi-sublattice magnets with electrically active magnetic excitations at room temperature give a direct possibility to transform one type of excitation into another in a terahertz time-domain. This is of crucial importance for the magnon-based spintronics as only the short-wavelength exchange magnons allow the signal processing on the nanoscale distance