Berlin 2015 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 16: Bio- and Molecular magnetism
MA 16.4: Vortrag
Dienstag, 17. März 2015, 10:15–10:30, EB 202
Quantum signatures of a molecular nanomagnet in direct magnetocaloric measurements — Joseph W. Sharples1, David Collison1, Eric J. L. McInnes1, Elias Palacios2, Marco Evangelisti2, and •Jürgen Schnack3 — 1Chemistry, The University of Manchester, UK — 2CSIC, Universidad de Zaragoza, Spain — 3Physics, Bielefeld University, Germany
Geometric spin frustration in low-dimensional materials, such as the two-dimensional kagome or triangular antiferromagnetic nets, can significantly enhance the change of the magnetic entropy and adiabatic temperature following a change in the applied magnetic field, that is, the magnetocaloric effect. In principle, an equivalent outcome should also be observable in certain high-symmetry zero-dimensional, that is, molecular, structures with frustrated topologies. Here we report experimental realization of this in a heptametallic gadolinium molecule. Adiabatic demagnetization experiments reach ∼ 200 mK, the first sub-Kelvin cooling with any molecular nanomagnet, and reveal isentropes (the constant entropy paths followed in the temperature-field plane) with a rich structure. The latter is shown to be a direct manifestation of the trigonal antiferromagnetic net structure, allowing study of frustration-enhanced magnetocaloric effects in a finite system.
J.W. Sharples, D. Collison, E.J.L. McInnes, J. Schnack, E. Palacios, M. Evangelisti, Nature Communications 5 (2014) 5321