Pressure dependence of the magnetic anisotropy in the single-molecule magnet Mn4O3Br(OAc)3(dbm)3 -: art. no. 172413

The anisotropy splitting in the ground state of the single-molecule magnet Mn4O3Br(OAc)(3)(dbm)(3) is studied by inelastic neutron scattering as a function of hydrostatic pressure. This allows a tuning of the anisotropy and thus the energy barrier for slow magnetization relaxation at low temperatures. The value of the negative axial anisotropy parameter D-cluster changes from -0.0627(1) meV at ambient to -0.0603(3) meV at 12 kbar pressure, and in the same pressure range the height of the energy barrier between up and down spins is reduced from 1.260(5) meV to 1.213(9) meV. Since the Mn-Br bond is significantly softer and thus more compressible than the Mn-O bonds, pressure induces a tilt of the single ion Mn3+ anisotropy axes, resulting in the net reduction of the axial cluster anisotropy.