title: Long-range ferromagnetic dipolar ordering of high-spin molecular clusters.
abstract: We report the first example of a transition to long-range magnetic order in a purely dipolarly interacting molecular magnet. For the magnetic cluster compound Mn6O4Br4(Et2dbm)6, the anisotropy experienced by the total spin S = 12 of each cluster is so small that spin-lattice relaxation remains fast down to the lowest temperatures, thus enabling dipolar order to occur within experimental times at T(c) = 0.16 K. In high magnetic fields, the relaxation rate becomes drastically reduced and the interplay between nuclear- and electron-spin lattice relaxation is revealed.
authors.affiliation: Kamerlingh Onnes Laboratory, Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Morello
authors.forename: F L
authors.initials: FL
authors.lastname: Mettes
authors.forename: F
authors.initials: F
authors.lastname: Luis
authors.forename: J F
authors.initials: JF
authors.lastname: Fernández
authors.forename: J
authors.initials: J
authors.lastname: Krzystek
authors.forename: G
authors.initials: G
authors.lastname: Aromí
authors.forename: G
authors.initials: G
authors.lastname: Christou
authors.forename: L J
authors.initials: LJ
authors.lastname: de Jongh