Pressure dependence of the magnetic anisotropy in the single-molecule magnet Mn4O3Br„OAc...3„dbm...3

The anisotropy splitting in the ground state of the single-molecule magnet Mn4O3BrsOAcd3sdbmd3 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 Dcluster changes from −0.0627s1d meV at ambient to −0.0603s3d 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 1.260s5d meV to 1.213s9d meV. Since the MnuBr bond is significantly softer and thus more compressible than the MnuO bonds, pressure induces a tilt of the single ion Mn3+ anisotropy axes, resulting in the net reduction of the axial cluster anisotropy.