We used site-selective and element-specific resonant inelastic x-ray scattering ͑RIXS͒ to study the electronic structure and the electron interaction effects in the molecular magnet ͓Mn 12 O 12 ͑CH 3 COO͒ 16 ͑H 2 O͒ 4 ͔ · 2CH 3 COOH · 4H 2 O, and compared the experimental data with the results of local spin density approximation +U electron structure calculations which include the on-site Coulomb interactions. We found a good agreement between theory and experiment for the Coulomb repulsion parameter U = 4 eV. In particular, the p-d band separation of 1.8 eV has been found from the RIXS spectra, which is in accordance with the calculations. Similarly, the positions of the peaks in the XPS spectra agree with the calculated densities of p and d states. Using the results of the electronic structure calculations, we determined the intramolecular exchange parameters, and used them for diagonalization of the Mn 12 spin Hamiltonian. The calculated exchanges gave the correct ground state with the total spin S = 10.

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. AbstractWe calculate the tunneling splittings in a Mn 12 magnetic molecule taking into account its internal many-spin structure. We discuss the precision and reliability of these calculations and show that restricting the basis (limiting the number of excitations taken into account) may lead to significant error (orders of magnitude) in the resulting tunneling splittings for the lowest energy levels, so that an intuitive picture of different decoupled energy scales does not hold in this case. ; and, at present, a substantial amount of reliable experimental data has been collected. Quantitative analysis of these experiments is a challenging theoretical problem involving fundamental issues about tunneling phenomena in mesoscopic magnetic systems. The basic prerequisite for solving this problem is our ability to evaluate accurately and reliably the energy splittings occurring as a result of tunneling between two (quasi) degenerate levels [7]. At present, carefully designed magnetic relaxation

Spin tunneling in molecular magnets has attracted much attention, however theoretical considerations of this phenomenon up to now have not taken into account the manyspin nature of molecular magnets. We present, to our knowledge, the first successful attempt of a realistic calculation of tunneling splittings for Mn12 molecules, thus achieving a quantitatively accurate many-spin description of a real molecular magnet in the energy interval ranging from about 100 K down to 10 −12 K. Comparison with the results of the standard single-spin model shows that many-spin effects affect the tunneling splittings considerably. The values of ground state splitting given by single-spin and many-spin models differ from each other by a factor of five. 75.50.Xx, 75.10.Dg, 75.45.+j, 75.40.Mg