Magnetic Relaxation Study on Single Crystals of Ni4 Single-Molecule Magnets
LI Yan-Rong1,2, LIU Hai-Qing1, LIU Ying1, SU Shao-Kui1, WANG Yun-Ping1
1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 1001902Department of Physics, University of Science and Technology of China, Hefei 230026
Magnetic Relaxation Study on Single Crystals of Ni4 Single-Molecule Magnets
LI Yan-Rong1,2, LIU Hai-Qing1, LIU Ying1, SU Shao-Kui1, WANG Yun-Ping1
1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 1001902Department of Physics, University of Science and Technology of China, Hefei 230026
摘要The ac susceptibility of single crystals of Ni4 single-molecule magnets is measured by a compensation measurement setup. The magnetic relaxation time calculated from the peak of the out-phase component of the susceptibility fits the Arrhenius law well and gives an effective spin-flipping energy barrier of Ueff=7.2K. This value is far below the classical activation energy barrier of U=14K, whereas it is close to the energy gap between the Sz=±4 and Sz=±3 doublets, which indicates that quantum tunneling between the Sz=3 and Sz=-3 states plays a key role in the magnetic relaxation. Therefore the relaxation process combines thermal activation and quantum tunneling. Also we deduce that the blocking temperature of Ni4 single-molecule magnets is lower than 0.3K by extrapolating the relaxation time plot, which ensures that this single-molecule magnet material enters a long-range magnetic ordered state instead of a spin glass state at 0.91K.
Abstract：The ac susceptibility of single crystals of Ni4 single-molecule magnets is measured by a compensation measurement setup. The magnetic relaxation time calculated from the peak of the out-phase component of the susceptibility fits the Arrhenius law well and gives an effective spin-flipping energy barrier of Ueff=7.2K. This value is far below the classical activation energy barrier of U=14K, whereas it is close to the energy gap between the Sz=±4 and Sz=±3 doublets, which indicates that quantum tunneling between the Sz=3 and Sz=-3 states plays a key role in the magnetic relaxation. Therefore the relaxation process combines thermal activation and quantum tunneling. Also we deduce that the blocking temperature of Ni4 single-molecule magnets is lower than 0.3K by extrapolating the relaxation time plot, which ensures that this single-molecule magnet material enters a long-range magnetic ordered state instead of a spin glass state at 0.91K.
(Diamagnetism, paramagnetism, and superparamagnetism)
引用本文:
LI Yan-Rong;LIU Hai-Qing;LIU Ying;SU Shao-Kui;WANG Yun-Ping. Magnetic Relaxation Study on Single Crystals of Ni4 Single-Molecule Magnets[J]. 中国物理快报, 2009, 26(7): 77504-077504.
LI Yan-Rong, LIU Hai-Qing, LIU Ying, SU Shao-Kui, WANG Yun-Ping. Magnetic Relaxation Study on Single Crystals of Ni4 Single-Molecule Magnets. Chin. Phys. Lett., 2009, 26(7): 77504-077504.
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2009, Vol. 26 
