title: Long-range ferromagnetism of Mn12 acetate single-molecule magnets under a transverse magnetic field.
abstract: We use neutron diffraction to probe the magnetization components of a crystal of Mn12 single-molecule magnets. Each of these molecules behaves, at low temperatures, as a nanomagnet with spin S = 10 and strong anisotropy along the crystallographic c axis. The application of a magnetic field H(perpendicular) perpendicular to c induces quantum tunneling between opposite spin orientations, enabling the spins to attain thermal equilibrium. For T approximately < 0.9(1) K, this equilibrium state shows spontaneous magnetization, indicating the onset of ferromagnetism. These long-range magnetic correlations nearly disappear for mu0H(perpendicular) approximately > 5.5 T, possibly suggesting the existence of a quantum critical point.
authors.affiliation: Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, 50009 Zaragoza, Spain. fluis@unizar.es
authors.forename: F
authors.initials: F
authors.lastname: Luis
authors.forename: J
authors.initials: J
authors.lastname: Campo
authors.forename: J
authors.initials: J
authors.lastname: Gómez
authors.forename: G J
authors.initials: GJ
authors.lastname: McIntyre
authors.forename: J
authors.initials: J
authors.lastname: Luzón
authors.forename: D
authors.initials: D
authors.lastname: Ruiz-Molina