[seminar] SEMINAR na IF-u u CETVRTAK, 14.10.2010.

[Ivica Zivkovic]

*Institut za fiziku, Bijenička cesta 46,*

*predavaonica u zgradi Mladen Paić*

*četvrtak, 14. listopada 2010, u 15:00 sati*

*Neutron scattering studies of weakly coupled*

*and weakly connected antiferromagnets

*

*Dr. Krunoslav Prša*

*Laboratory for Solid State Ph**ysics *

*ETH Zürich Hönggerberg, Switzerland*


/*E-mail: */_/*kprsa at phys.ethz.ch*/_

*Antiferromagnetic insulators at low temperatures offer a clean arena to 
study non--**semiclassical phenomena because the character of 
interactions is usually known. These quantum effects are expected to 
increase by lowering the couplings or connectivity between the magnetic 
moments. Magnetic excitations, which can be easily measured by the 
neutron spectroscopy technique, are particularly sensitive to quantum 
effects. We here study the weakly coupled tetrahedra system Cu2Te2O5X2 
(X=Cl, Br) and weakly connected Cu3TeO6 system. In the Cu2Te2O5X2 system 
we observed an unusual situation where an anomalously weak low--energy 
Goldstone-- like mode is accompanied by a strong higher energy gapped 
mode. We propose that the origin of the discrepancy lies in the quantum 
fluctuations originating between the tetrahedra, which were not taken 
into account by the theory. In the "spin--web" lattice system Cu3TeO6, 
we show that a strong magnon--phonon coupling in this system 
significantly changes the properties of the spectrum.*


*Voditelji seminara IF-a: Berislav Horvatić & Ivica Živković*



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