Spin-frustrated trinuclear Cu(II) clusters with mixing of 2(S = 1/2) and S = 3/2 states by antisymmetric exchange. 1. Dzialoshinsky-Moriya exchange contribution to zero-field splitting of the S = 3/2 state

The mixing of the spin-frustrated 2(S = 1/2) and S = 3/2 states by the Dzialoshinsky-Moriya (DM) exchange is considered for the Cu 3(II) clusters with strong DM exchange coupling. In the antiferromagnetic Cu 3 clusters with strong DM interaction, the 2(S = 1/2)-S = 3/2 mixing by the in-plane DM exchange ( G x ) results in the large positive contribution 2 D DM > 0 to the axial zero-field splitting (ZFS) 2 D of the S = 3/2 state. The correlations between the ZFS 2 D DM of the excited S = 3/2 state, sign of G z and chirality of the ground-state were obtained. In the isosceles Cu 3 clusters, the in-plane DM exchange mixing results in the rhombic magnetic anisotropy of the S = 3/2 state. Large distortions result in an inequality of the pair DM parameters, that leads to an additional magnetic anisotropy of the S = 3/2 state. In the {Cu 3} nanomagnet, the in-plane DM exchange (Gx, Gy) mixing results in the 58% contribution 2 D DM to the observed ZFS 2 D of the S = 3/2 state. The DM exchange and distortions explain the experimental observation that the intensities of the electron paramagnetic resonance (EPR) transitions arising from the 2(S = 1/2) group of levels of the {Cu 3} nanomagnet are comparable to each other and are 1 order of magnitude weaker than that of the S = 3/2 state. In the ferromagnetic Cu 3 clusters, the in-plane DM exchange mixing of the excited 2(S = 1/2) and the ground S = 3/2 states results in the large negative DM exchange contribution 2 D DM' < 0 to the axial ZFS 2 D of the ground S = 3/2 state.