Exchange constants and spin dynamics in Mn12-acetate
نویسندگان
چکیده
We have obtained new inelastic neutron scattering (INS) data for the molecular magnet Mn12-acetate which exhibit at least six magnetic peaks in the energy range 5–35meV. These are compared with a microscopic Heisenberg model for the 12 quantum spins localised on the Mn ions, coupled by four inequivalent magnetic exchange constants. A fit to the magnetic susceptibility under the constraint that the spin of the ground state be S 1⁄4 10 yields two dominant exchange constants of very similar value, J1 J2 65K ( 5:5meV), and two smaller exchange constants J3 and J4: We compute the low-lying excitations by exact numerical diagonalisation and demonstrate that the parameters determined from the ground state and susceptibility fit provide qualitative agreement with the excitations observed by INS. PACS: 75.30.Et; 75.50.Xx; 78.70.Nx
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