ic7b02453_si_001.pdf (1.36 MB)
Suppression of Magnetic Quantum Tunneling in a Chiral Single-Molecule Magnet by Ferromagnetic Interactions
journal contribution
posted on 2017-11-30, 19:20 authored by Kai-Alexander Lippert, Chandan Mukherjee, Jan-Philipp Broschinski, Yvonne Lippert, Stephan Walleck, Anja Stammler, Hartmut Bögge, Jürgen Schnack, Thorsten GlaserSingle-molecule
magnets (SMMs) retain a magnetization without applied magnetic field
for a decent time due to an energy barrier U for
spin-reversal. Despite the success to increase U,
the difficult to control magnetic quantum tunneling often leads to
a decreased effective barrier Ueff and
a fast relaxation. Here, we demonstrate the influence of the exchange
coupling on the tunneling probability in two heptanuclear SMMs hosting
the same spin-system with the same high spin ground state St = 21/2. A chirality-induced symmetry reduction
leads to a switch of the MnIII–MnIII exchange
from antiferromagnetic in the achiral SMM [MnIII6CrIII]3+ to ferromagnetic
in the new chiral SMM RR[MnIII6CrIII]3+. Multispin
Hamiltonian analysis by full-matrix diagonalization demonstrates that
the ferromagnetic interactions in RR[MnIII6CrIII]3+ enforce a well-defined St = 21/2
ground state with substantially less mixing of MS substates in contrast to [MnIII6CrIII]3+ and no tunneling pathways
below the top of the energy barrier. This is experimentally verified
as Ueff is smaller than the calculated
energy barrier U in [MnIII6CrIII]3+ due to tunneling pathways,
whereas Ueff equals U in RR[MnIII6CrIII]3+ demonstrating the
absence of quantum tunneling.