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Ferromagnetic coupling and magnetic anisotropy in molecular Ni(II) squares

R. Koch·O. Waldmann·P. Mueller·U. Reimann·R. W. Saalfrank
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Abstract

We investigated the magnetic properties of two isostructural Ni(II) metal complexes [Ni4Lb8] and [Ni4Lc8]. In each molecule the four Ni(II) centers form almost perfect regular squares. Magnetic coupling and anisotropy of single crystals were examined by magnetization measurements and in particular by high-field torque magnetometry at low temperatures. The data were analyzed in terms of an effective spin Hamiltonian appropriate for Ni(II) centers. For both compounds, we found a weak intramolecular ferromagnetic coupling of the four Ni(II) spins and sizable single-ion anisotropies of the easy-axis type. The coupling strengths are roughly identical for both compounds, whereas the zero-field-splitting parameters are significantly different. Possible reasons for this observation are discussed.

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R. Koch, O. Waldmann, P. Mueller, U. Reimann, R. W. Saalfrank. 2003-01-21. Ferromagnetic coupling and magnetic anisotropy in molecular Ni(II) squares. https://doi.org/10.1103/physrevb.67.094407

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