Dresden 2017 – scientific programme
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MA: Fachverband Magnetismus
MA 20: Bio- and Molecular Magnetism
MA 20.1: Talk
Tuesday, March 21, 2017, 09:30–09:45, HSZ 301
Changing the Molecular Conformation of Endohedral Rare Earth Single-Molecule Magnets with Magnetic Torque — •Aram Kostanyan1, Rasmus Westerström2, Yang Zhang3, Alexey Popov3, and Thomas Greber1 — 1Physik-Institut, Uni Zürich, Winterthurerstr. 190,8057 Zürich, Switzerland — 2Division of Synchrotron Radiation Research, Department of Physics, Lund University, Lund, Sweden — 3Nanoscale Chemistry, IFW Dresden,Helmholtzstr. 20, 01069, Dresden, Germany
The endohedral unit of endohedral fullerenes exhibits thermally activated hopping motion between low-energy conformations. The motion ceases out at low temperatures locking the unit in a random state.
For single-molecule magnet HoLu2N@C80, the magnetic moment of Ho is aligned with the Ho-N axis due to strong ligand field imposed by the N3− ion. If the external magnetic field applies a torque on the magnetic moment of the Ho3+ ion it can be transferred to the encapsulated unit.
Field and temperature dependent measurements show a conformational change by means of magnetic torque on a single magnetic moment. At 1.8 K, the in-field cooled sample shows a magnetization curve that exceeds that of the zero-field cooled one. The difference does not scale with a single factor and increases with decreasing temperature sweep rate.
By means of a first order kinetics model, it is possible to determine the attempt frequency and activation energy for the hopping motion. It also allows to understand the non-linear field dependence of the effect.