MAGNETIC-PROPERTIES OF A NEW SPIN CLUSTER TOPOLOGY WITH HIGH-SPIN GROUND-STATE - THE SPIN CLUSTER -3(III)(TEAH)(3)(TEA)(3)](CLO4)(2)CENTER-DOT-3MEOH

The new spin cluster [(Mn4Mn3III)-Mn-II(teaH)(3)(tea)(3)](ClO4)(2) x 3 MeOH realizes a topological structure of mixed-valence manganese clust ers which is especially favorable for a high-spin ground state. The ma gnetic properties of the spin cluster are studied numerically by exact diagonalization of the spin Hamiltonian. By magnetic susceptibility t wo exchange constants are found: J(1)/k(B) = -1.28 K and J(2)/k(B) = 4.25 K, which lead to a S = 11 high-spin ground state. Electron spin r esonance (ESR) measurements at three frequencies 95, 190 and 285 GHz c onfirm the large spin of the ground state..and reveal, an Ising anisot ropy of the ground state which is characterized by the spin Hamiltonia n H = alpha(S-z)(2) + beta(S-z)(4) with alpha/h.c. = -0.08 cm(-1) and beta = -2.1 x 10(-4) cm(-1) Ac-susceptibility shows thermally activate d relaxation of the magnetization for temperatures above T = 1 K with an activation energy of Delta E/k(B) = -19.5 K and a relaxation time o f tau(0) approximate to 10(-8) s.