Abstract
We report the results of systematic experimental and theoretical studies of two closely related species of magnetic molecules of the type where each molecule includes a pair of triangles of exchange-coupled vanadyl spin ions. The experimental studies include the temperature dependence of the low-field susceptibility from room temperature down to 2 K, the dependence of the magnetization on magnetic field up to 60 T for several low temperatures, the temperature dependence of the magnetic contribution to the specific heat, and the and nuclear magnetic resonance spin-lattice relaxation rates This body of experimental data is accurately reproduced for both compounds by a Heisenberg model for two identical uncoupled triangles of spins; in each triangle, the spins interact via isotropic antiferromagnetic exchange, where two of the three V-V interactions have exchange constants that are equal and an order of magnitude larger than the third; the ground-state eigenfunction has total spin quantum number for magnetic fields below a predicted critical field and for fields above
- Received 19 February 2002
DOI:https://doi.org/10.1103/PhysRevB.66.054407
©2002 American Physical Society