A Novel Ni4 Complex Exhibiting Microsecond Quantum Tunneling of the Magnetization

被引:33
作者
Aromi, Guillem [1 ]
Bouwman, Elisabeth [2 ]
Burzuri, Enrique [3 ,4 ]
Carbonera, Chiara [3 ,4 ]
Krzystek, J. [5 ]
Luis, Fernando [3 ,4 ]
Schlegel, Christoph [6 ]
van Slageren, Joris [6 ,7 ]
Tanase, Stefania [2 ]
Teat, Simon J. [8 ,9 ]
机构
[1] Univ Barcelona, Fac Quim, Dept Quim Inorgan, E-08028 Barcelona, Spain
[2] Leiden Univ, Leiden Inst Chem, Gorlaeus Labs, NL-2300 RA Leiden, Netherlands
[3] Univ Zaragoza, CSIC, Inst Ciencia Mat Aragon, E-50009 Zaragoza, Spain
[4] Dept Fis Mat Condensada, Zaragoza 50009, Spain
[5] Florida State Univ, Natl High Magnet Field Lab, Tallahassee, FL 32310 USA
[6] Univ Stuttgart, Inst Phys 1, D-70550 Stuttgart, Germany
[7] Univ Nottingham, Sch Chem, Nottingham NG7 2RD, England
[8] SERC, Daresbury Lab, Warrington WA4 4AD, Cheshire, England
[9] Univ Calif Berkeley, Lawrence Berkeley Lab, Light Source, Berkeley, CA 94720 USA
基金
美国国家科学基金会;
关键词
cluster compounds; magnetic properties; nickel; quantum tunneling; relaxation;
D O I
10.1002/chem.200801450
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
A highly asymmetric N-II cluster [Ni-4(OH)(OMe)(3)(Hphpz)(4)(MeOH)(3)](MeOH) (1) (H(2)phpz = 3-methyl-5-(2-hydroxyphenyl)pyrazole) has been prepared and its structure determined by means of single-crystal X-ray diffraction by using synchrotron radiation. Variable-temperature bulk-magnetization measurements show that the complex exhibits intramolecular ferromagnetic interactions leading to a spin ground state S=4 with close-lying excited states. Magnetization and high-frequency EPR measurements suggest the presence of sizable Ising-type magnetic anisotropy, with zero-field splitting parameters D = -0.263 cm(-1) and E = 0.04 cm(-1) for the spin ground state, and an isotropic g value of 2.25. The presence of both axial and transverse anisotropy was confirmed through low-temperature specific heat determinations down to 300 mK, but no slow relaxation of the magnetization was observed by AC measurements down to 1.8 K. Interestingly, AC susceptibility measurements down to temperatures as low as 23 mK showed no indication of slow relaxation of the magnetization in 1. Thus, despite the presence of an anisotropy barrier (U approximate to 4.21 cm(-1) for the purely axial limit), the magnetization relaxation remains extremely fast down to the lowest temperatures. The estimated quantum tunneling rate, Gamma > 0.667 MHz, makes this complex a prime candidate for observation of coherent tunneling of the magnetization.
引用
收藏
页码:11158 / 11166
页数:9
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