Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 3: Spin-Systeme und itinerante Magnete

TT 3.5: Vortrag

Montag, 8. März 2004, 10:30–10:45, H18

Magnetocaloric effect in one-dimensional quantum spin models — •A. Honecker¹ and M.E. Zhitomirsky² — ¹Universität Hannover, Institut für Theoretische Physik, Appelstraße 2, 30167 Hannover — ²Commissariat à l’Énergie Atomique, DMS/DRFMC/SPSMS, 38054 Grenoble, Cedex 9 France

An external magnetic field induces changes in the entropy of a quantum spin system at finite temperatures which can be rather large in particular if the spin system is geometrically frustrated. This implies a magnetocaloric effect, i.e. a change in temperature during an adiabatic (de)magnetization process. Here we study several examples of one-dimensional spin models with low spin quantum number (S=1/2 and 1) employing exact diagonalization and the Jordan-Wigner transformation. During an adiabatic (de)magnetization process the temperature drops in the vicinity of a field-induced zero-temperature quantum phase transition. Comparing different levels of frustration, we find that more frustrated systems cool down to lower temperatures. Our study demonstrates that frustrated quantum spin systems are promisimng alternative refrigerant materials for low-temperature magnetic refrigeration.