title: Magnetic and 57Fe Mössbauer study of the single molecule magnet behavior of a Dy3Fe7 coordination cluster.
abstract: The reaction between N-methydiethanolamine (mdeaH(2)), benzoic acid, FeCl(3), and DyCl(3) yields a decanuclear coordination cluster, [Dy(3)Fe(7)(mu(4)-O)(2)(mu(3)-OH)(2)(mdea)(7)(mu-benzoate)(4)(N(3))(6)] x 2 H(2)O x 7 CH(3)OH (1) whose single crystal structure exhibits three and seven crystallographically distinct Dy(III) and Fe(III) ions; six of the Fe(III) ions are pseudo-octahedrally coordinated, whereas the seventh has a trigonal-bipyramidal coordination geometry. Both direct current (dc) and alternating current (ac) magnetic susceptibility studies indicate that, upon cooling, intracluster antiferromagnetic interactions are dominant in 1, yielding a ferrimagnetic spin arrangement. The out-of-phase (chi'') ac susceptibility reveals that 1 undergoes a slow relaxation of its magnetization mainly resulting from the anisotropy of the Dy(III) ions. This slow relaxation has been confirmed both by magnetization measurements on an oriented single crystal of 1 and by the observation of hysteresis loops below 1.9 K. The macroscopic magnetic studies yield an effective energy barrier, U(eff), of 33.4 K for this relaxation, a barrier that is the highest yet reported for a lanthanide(III)-Fe(III) single molecule magnet. The (57)Fe Mössbauer spectra of 1 obtained between 3 and 35 K are consistent with the presence of Fe(III) intracluster antiferromagnetic coupling with slow magnetic relaxation relative to the Larmor precession time, thus confirming, on a microscopic scale, the presence of a barrier to the magnetic relaxation below 35 K. Between 55 and 295 K the Mössbauer spectra reveal paramagnetic behavior with six partially resolved quadrupole doublets, one for the trigonal-bipyramidal Fe(III) site and five for the six pseudo-octahedral Fe(III) sites.
authors.affiliation: Institut für Anorganische Chemie, Karlsruhe Institute of Technology, University of Karlsruhe, Engesserstrasse 15, D-76131 Karlsruhe, Germany.
authors.forename: Ghulam
authors.initials: G
authors.lastname: Abbas
authors.forename: Yanhua
authors.initials: Y
authors.lastname: Lan
authors.forename: Valeriu
authors.initials: V
authors.lastname: Mereacre
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wernsdorfer
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Clérac
authors.forename: Gernot
authors.initials: G
authors.lastname: Buth
authors.forename: Moulay T
authors.initials: MT
authors.lastname: Sougrati
authors.forename: Fernande
authors.initials: F
authors.lastname: Grandjean
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Long
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Anson
authors.forename: Annie K
authors.initials: AK
authors.lastname: Powell