CPM Seminar

From single molecule magnetism to long range ferromagnetism in a giant spin molecular magnet

O. Moze

Dipartimento di Fisica
Università di Modena e Reggio Emilia

The molecular nanomagnet Hpyr[Fe₁₇O₁₆(OH)₁₂(py)₁₂Br₄]Br₄ ("Fe₁₇") has an extraordinarily large and well-defined cluster spin ground-state of S = 35/2 at low temperatures, and an axial molecular magnetic anisotropy of only D = -0.02 K. Long-range magnetic order in this system is induced below 1 K via dipolar interactions between the large molecular spins. This magnetic order has been investigated in detail by neutron powder diffraction experiments performed on a polycrystalline sample of deuterated Fe₁₇ in zero applied magnetic field. The temperature-dependence of the long-range magnetic order parameter has been tracked and is well accounted for within mean field theory. The ferromagnetic order between giant molecular spins, which is along the crystallographic c-axis, as determined by the neutron diffraction experiments, is in agreement with ground state dipolar energy calculations. In addition to details of the neutron diffraction investigation, the bulk susceptibility, magnetization and magnetic field dependence of the specific heat will be presented and discussed.