Exchange Interactions at the Origin of Slow Relaxation of the Magnetization in {TbCu3} and {DyCu3} Single-Molecule Magnets

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• 作者：Fraser J. Kettles ; Victoria A. Milway ; Floriana Tuna ; Rafael Valiente ; Lynne H. Thomas ; Wolfgang Wernsdorfer ; Stefan T. Ochsenbein ; Mark Murrie
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：September 2, 2014
• 年：2014
• 卷：53
• 期：17
• 页码：8970-8978
• 全文大小：612K
• ISSN：1520-510X

文摘

New {TbCu₃} and {DyCu₃} single-molecule magnets (SMMs) containing a low-symmetry Ln^III center (shape measurements relative to a trigonal dodecahedron and biaugmented trigonal prism are 2.2鈥?.3) surrounded by three Cu^II metalloligands are reported. SMM behavior is confirmed by frequency-dependent out-of-phase ac susceptibility signals and single-crystal temperature and sweep rate dependent hysteresis loops. The ferromagnetic exchange interactions between the central Ln^III ion and the three Cu^II ions could be accurately measured by inelastic neutron scattering (INS) spectroscopy and modeled effectively. The excitations observed by INS correspond to flipping of Cu^II spins and appear at energies similar to the thermodynamic barrier for relaxation of the magnetization, 鈭?5鈥?0 K, and are thus at the origin of the SMM behavior. The magnetic quantum number M_tot of the cluster ground state of {DyCu₃} is an integer, whereas it is a half-integer for {TbCu₃}, which explains their vastly different quantum tunneling of the magnetization behavior despite similar energy barriers.