A wheel-shaped single-molecule magnet of [Mn3 IIMn4111]: Quantum tunneling of magnetization under static and pulse magnetic fields

Satoshi Koizumi, Masayuki Nihei, Takuya Shiga, Motohiro Nakano, Hiroyuki Nojiri, Roland Bircher, Oliver Waldmann, Stefan T. Ochsenbein, Hans U. Güdel, Felix Fernandez-Alonso, Hiroki Oshio

Research output: Contribution to journalArticlepeer-review

74 Citations (Scopus)

Abstract

The reaction of N-(2-hydroxy-5-nitrobenzyl)iminodiethanol (= H 3(5-NO2-hbide)) with Mn(OAc)2·4H 2O in methanol, followed by recrystallization from 1,2-dichloroethane, yielded a wheel-shaped single-molecule magnet (SMM) of [Mn3IIMn4III(5-NO 2-hbide)6]·5C2H4Cl 2 (1). In 1, seven manganese ions are linked by six tri-anionic ligands and form the wheel in which the two manganese ions on the rim and the one in the center are MnII and the other four manganese ions are MnIII ions. Powder magnetic susceptibility measurements showed a gradual increase with XmT values as the temperature was lowered, reaching a maximum value of 53.9 emu mol-1 K. Analyses of magnetic susceptibility data suggested a spin ground state of S=19/2. The zero-field splitting parameters of D and B40 were estimated to be -0.283(1) K and -1.64(1) × 10-5 K, respectively, by high-field EPR measurements (HF-EPR). The anisotropic parameters agreed with those estimated from magnetization and inelastic neutron scattering experiments. AC magnetic susceptibility measurements showed frequency-dependent in- and out-of-phase signals, characteristic datafor an SMM, and an Arrhenius plot of the relaxation time gave a re-orientation energy barrier (δE) of 18.1 K and a pre-exponential factor of 1.63 × 10-7 s. Magnetization experiments on aligned single crystals below 0.7 K showed a stepped hysteresis loop, confirming the occurrence of quantum tunneling of the on magnetization (QTM). QTM was, on the other hand, suppressed by rapid sweeps of the magnetic field even at 0.5 K. The sweep-rate dependence of the spin flips can be understood by considering the Landau-Zener-Stückelberg (LZS) model.

Original languageEnglish
Pages (from-to)8445-8453
Number of pages9
JournalChemistry - A European Journal
Volume13
Issue number30
DOIs
Publication statusPublished - 2007

Keywords

  • Magnetic properties
  • Manganese
  • Mixed-valent compounds

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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