FIR-magnetospectroscopy on molecular magnets

FIR-magnetospectroscopy has been performed on nano-scale molecular magnets to study their spin Hamiltonian parameters and symmetries. The first case is the characterization of high spin molecule Mn₁₁Crac[Mn₁₁Cr(O₂CCH₃)₁₆(H₂O)₄]·4H₂O)] with ferromagnetic ground state, which is made by Cr doping into the most famous ferromagnetic cluster Mn₁₂ac with S=10 ground state. We found that Mn₁₁Crac is the spin-odd cluster(S=19/2) and that the anisotropy parameter is nearly identical to that of Mn₁₂ac. A comparative study of those clusters is very useful to explore spin parity effect in quantum tunnelling. As the second example, we investigate a four-spin-ring with singlet ground state. We observed forbidden transitions between the ground state and the excited states, which uncovers the nature of the tunnelling gaps caused by the mixing among the quantized levels.