Investigation of a ring single molecular magnet Mn$_6$R$_6$ in megagauss fields

The dependence of the magnetic susceptibility on the magnetic field is investigated for the single molecular magnet [Mn(hfac)$_2$NITPh]$_6$. The spikes of the susceptibility detected in a magnetic field ranging from 90 T to 285 T are interpreted as a manifestation of magnetic quantum jumps under spins reorientation from ferrimagnetic to ferromagnetic structure. The characteristic feature of the single molecular magnet Mn$_6$ R$_6$ is a deficiency of pair Heisenberg exchange interactions for the description of its magnetic properties in high magnetic fields. The comparison of the experimental data with the results of theoretical calculations allows us to prove the existence of strong three-spin interaction in this molecular cluster and to determine the values of exchange constants. For the calculation of the ground state spin structure the modified Lanczos method is used.