title: Quantum signatures of a molecular nanomagnet in direct magnetocaloric measurements.
abstract: 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.
authors.affiliation: School of Chemistry and Photon Science Institute, The University of Manchester, Manchester M13 9PL, UK.
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Sharples
authors.affiliation: School of Chemistry and Photon Science Institute, The University of Manchester, Manchester M13 9PL, UK.
authors.forename: David
authors.initials: D
authors.lastname: Collison
authors.affiliation: School of Chemistry and Photon Science Institute, The University of Manchester, Manchester M13 9PL, UK.
authors.forename: Eric J L
authors.initials: EJ
authors.lastname: McInnes
authors.affiliation: Faculty of Physics, Bielefeld University, PO box 100131, D-33501 Bielefeld, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Schnack
authors.affiliation: Departamento de Física de la Materia Condensada and Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain.
authors.forename: Elias
authors.initials: E
authors.lastname: Palacios
authors.affiliation: Departamento de Física de la Materia Condensada and Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain.
authors.forename: Marco
authors.initials: M
authors.lastname: Evangelisti