Are the magnetic molecule Mo12O30(OH)10H2[Ni(H2O)3]4 and its isostructural relatives showing magnetostriction?

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Magnetic molecules show a variety of interesting phenomena like tunneling of the magnetization or a hysteresis in a varying field. Magnetostriction does not belong to the effects observed on the molecular level so far. Nevertheless, we regard magnetostriction to be an ubiquitous phenomenon with magnetic molecules. Experimental results, obtained by our experimental collaborators in Ames (USA) and Okayama (Japan), together with preliminary theoretical work in our group, suggest that the magnetic molecule Ni4 shows a pronounced dependence of the exchange parameter J on the applied magnetic field. Such dependence usually results from magnetostriction which alters the bond length and angle between the magnetic centers. The aim of the project therefore is to understand the observed dependencies and to investigate whether a possibly field-dependent anisotropy or a field-dependent exchange parameter can explain the observed data. The final aim is to design an effective Hamiltonian. Crucial questions are whether the effect depends directly on the applied field or on the magnetization of the molecule as well as whether there is an orientational dependence. The project will be accompanied by attempts of our experimental partners to measure the magnetostriction directly.