Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 17: Symposium Quantum Magnetism in Molecule-based Materials

TT 17.4: Fachvortrag

Montag, 7. März 2005, 12:00–12:30, TU H104

Magnetocaloric effect in frustrated and molecular magnets — •Andreas Honecker — Technische Universität Braunschweig, Institut für Theoretische Physik, 38106 Braunschweig, Germany

Due to the magnetocaloric effect, adiabatic changes of the field applied to a magnet yield a change of temperature. Adiabatic demagnetization of a paramagnetic salt was the first method to achieve temperatures below 1K. Recently, there has been renewed interest in cooling by adiabatic demagnetization for room-temperature applications. Also low-temperature records are still established by this method.

We discuss recent theoretical results for the magnetocaloric effect in the vicinity of field-induced quantum phase transitions in correlated and molecular magnets. Geometrically frustrated magnets are of special interest since they exhibit large entropies at low temperatures, promising a large magnetocaloric effect. In particular a comparative study of different one-dimensional quantum magnets shows that lower temperatures can indeed be achieved by adiabatic (de)magnetization of a frustrated system as compared to a non-frustrated one. Finally, we discuss potential applications of frustrated quantum magnets for efficient low-temperature magnetic refrigeration.