R. Basler, G. Chaboussant, C. Cañada-Vilalta, G. Christou, H. Mutka, S. Janssen, F. Altorfer and H.-U. Güdel
Magnetic and inelastic neutron scattering studies of a frustrated tetranuclear Mn³⁺ butterfly-type cluster
Polyhedron 22, 2471-2479 (2003)                 

Abstract: We report on the magnetic properties of the tetranuclear metallic cluster [Mn₄O₂(O₂CPh)₆(dpm)₂]. Using susceptibility, magnetization and inelastic neutron scattering (INS) spectroscopy we have determined the exchange and anisotropy parameters. The four Mn³⁺ (S=2) form a tetranuclear cluster with butterfly-type geometry. The two core Mn³⁺ ions are strongly antiferromagnetically coupled with J_b=-4.8±0.1 meV. The outer Mn³⁺ ions are loosely coupled to the core spins via two different weak interactions, ferromagnetic and antiferromagnetic, respectively: J_w1=+0.1±0.01 meV and J_w2=-0.1±0.01 meV. In addition, the octahedrally coordinated outer Mn³⁺ ions experience a large single-ion anisotropy DS_z² with D=-0.47±0.01 meV due to a strong distortion of the MnO₆ octahedra. The Landé g-factor is g=1.94±0.03. Frustration effects and competitive interactions lead to remarkable magnetic properties which cannot be unambiguously interpreted without the additional information from INS.