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Thermal-transport and magnetic properties of highly frustrated magnets

English title Thermal-transport and magnetic properties of highly frustrated magnets
Applicant Forro Laszlo
Number 111044
Funding scheme SCOPES
Research institution Laboratoire de nanostructures et nouveaux matériaux électroniques EPFL - SB - IPMC - LNNME
Institution of higher education EPF Lausanne - EPFL
Main discipline Condensed Matter Physics
Start/End 01.11.2005 - 31.10.2008
Approved amount 57'550.00
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All Disciplines (2)

Discipline
Condensed Matter Physics
Theoretical Physics

Keywords (5)

Thermal-transport properties; Magnetism; Correlated electrons; Frustration; Spin liquid

Lay Summary (English)

Lead
Lay summary
In last several years a rather great deal of the scientific attention was devoted to the investigation of the magnetic geometrically-frustrated systems. Geometrical frustration is a phenomenon when energy minimum and magnetically preferred spin interaction can not be established at the same time. The typical example of the geometrical frustrated systems is tetrahedron-base pyrochlore-like structure. One of the experimental realizations of the geometrically frustration exists in copper-tellurides of the general formula Cu2Te2O5Cl2-xBrx (0 < x < 2) and spin ices A2B2O7 (A is a rare earth element and B a transition metal). In both systems there is interplay between orders of the short and long range. Short range order is achieved by quantum interactions of the antiferromagnetic origin, while the tetrahedral structure frustrates the system. Inter-tetrahedral interaction in the copper-tellurides yields to the magnetic phase transition below 20 K with the formation of magnetically ordered state made of helically ordered spins with a period incommensurate to the crystal lattice. Copper-telluride compounds are close to the quantum criticality limit, as seen from the magnetization measurements. Dipole long-range interaction in spin-ices makes the overall interaction ferromagnetic. To the lowest experimentally reached temperatures, spin-ices do not exhibit magnetic ordering and spins freeze below some temperature. The questions of the origin and the nature of the magnetic phase transition and the proximity to the quantum criticality are still unresolved for copper-tellurides. In the case of spin-ices, the influence of the interplay between short- and long-range orders to the spin-ice-state formation is not resolved.The objective of the proposed JRP project is to widen the knowledge of the magnetic phase transition in copper-tellurides and to get an insight into the mechanisms leading to the spin freezing in spin-ices. In that sense the consortium will join efforts and available facilities to produce single-crystal samples of the highest possible quality. Their investigation will be done by means of the electron spin resonance (ESR) and magneto-thermal transport measurements.
Direct link to Lay Summary Last update: 21.02.2013

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