[Zurück]

B. Wolf, Y. Tsui, D. Jaiswal-Nagar, U. Tutsch, A. Honecker, K. Removic-Langer, G. Hoffmann, A. Prokofiev, W. Assmus, G. Donath, M. Lang:
"Magnetocaloric effect and magnetic cooling near a field-induced quantum-critical point";
PNAS - Proceedings of the National Academy of Sciences of the United States of America, 108 (2011), 18; S. 6862 - 6866.

The presence of a quantum-critical point (QCP) can significantly
affect the thermodynamic properties of a material at finite temperatures
T. This is reflected, e.g., in the entropy landscape SðT,rÞ
in the vicinity of a QCP, yielding particularly strong variations for
varying the tuning parameter r such as pressure or magnetic field
B. Here we report on the determination of the critical enhancement
of ∂S∕∂B near a B-induced QCP via absolute measurements of the
magnetocaloric effect (MCE), ð∂T∕∂BÞ
S and demonstrate that the
accumulation of entropy around the QCP can be used for efficient
low-temperature magnetic cooling. Our proof of principle is based
on measurements and theoretical calculations of the MCE and the
cooling performance for a Cu2þ-containing coordination polymer,
which is a very good realization of a spin-½ antiferromagnetic
Heisenberg chain-one of the simplest quantum-critical systems.

http://dx.doi.org/10.1073/pnas.1017047108