Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Modena e Reggio Emilia & INSTM RU of Modena and Reggio Emilia, via G. Campi 183, 41125 Modena, Italy.
Phys Chem Chem Phys. 2014 Aug 28;16(32):17220-30. doi: 10.1039/c4cp02462a.
Single-crystal torque magnetometry performed on weakly-coupled polynuclear systems provides access to a complete description of single-site anisotropy tensors. Variable-temperature, variable-field torque magnetometry was used to investigate triiron(III) complex [Fe3La(tea)2(dpm)6] (Fe3La), a lanthanum(III)-centred variant of tetrairon(III) single molecule magnets (Fe4) (H3tea = triethanolamine, Hdpm = dipivaloylmethane). Due to the presence of the diamagnetic lanthanoid, magnetic interactions among iron(III) ions (si = 5/2) are very weak (<0.1 cm(−1)) and the magnetic response of Fe3La is predominantly determined by single-site anisotropies. The local anisotropy tensors were found to have Di > 0 and to be quasi-axial with |Ei/Di| ~ 0.05. Their hard axes form an angle of approximately 70° with the threefold molecular axis, which therefore corresponds to an easy magnetic direction for the molecule. The resulting picture was supported by a High Frequency EPR investigation and by DFT calculations. Our study confirms that the array of peripheral iron(III) centres provides substantially noncollinear anisotropy contributions to the ground state of Fe4 complexes, which are of current interest in molecular magnetism and spintronics.
在弱耦合多核体系上进行单晶转矩磁强计测量，可以获得单个位置各向异性张量的完整描述。采用变温变场转矩磁强计研究了三铁（III）配合物[Fe3La(tea)2(dpm)6]（Fe3La），这是四铁（III）单分子磁体（Fe4）的镧（III）中心变体（H3tea = 三乙醇胺，Hdpm = 双（2,4,4-三甲基戊基）过氧化物）。由于存在抗磁性镧系元素，铁（III）离子（si = 5/2）之间的磁相互作用非常弱（<0.1 cm−1），Fe3La 的磁响应主要由单位置各向异性决定。发现局部各向异性张量具有 Di > 0，并且具有准轴向性，|Ei/Di|~0.05。它们的硬轴与三倍分子轴形成约 70°的角度，因此对于分子来说是一个容易磁化的方向。高频 EPR 研究和 DFT 计算支持了这一结果。我们的研究证实，外围铁（III）中心的排列为 Fe4 配合物的基态提供了实质上非共线的各向异性贡献，这在当前的分子磁学和自旋电子学中引起了关注。
