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

磁性分子表现出各种有趣的现象，如磁化隧穿或变化磁场中的磁滞现象。磁致伸缩不属于迄今为止在分子水平上观察到的效应。然而，我们认为磁致伸缩是一个普遍存在的现象与磁性分子。实验结果，我们的实验合作者在艾姆斯（美国）和冈山（日本），在我们的小组的初步理论工作一起，表明磁性分子Ni 4显示出显着的交换参数J上施加的磁场的依赖性。这种依赖性通常是由磁致伸缩引起的，磁致伸缩改变了键长和磁中心之间的角度。因此，该项目的目的是了解所观察到的依赖关系，并调查是否可能依赖于场的各向异性或依赖于场的交换参数可以解释所观察到的数据。最终目的是设计一个有效的哈密顿量。关键的问题是，这种效应是否直接取决于外加磁场或分子的磁化强度，以及是否存在取向依赖性。该项目将伴随着我们的实验合作伙伴尝试直接测量磁致伸缩。

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.