title: Intense low-energy ferromagnetic fluctuations in the antiferromagnetic heavy-fermion metal CeB6.
abstract: Heavy-fermion metals exhibit a plethora of low-temperature ordering phenomena . Among these are the so-called hidden-order phases that, in contrast to conventional magnetic order, are invisible to standard neutron diffraction experiments. One of the structurally most simple hidden-order compounds, CeB6, has been intensively studied for an elusive phase that was attributed to the antiferroquadrupolar ordering of cerium-4f moments . As the ground state of CeB6 is characterized by a more conventional antiferromagnetic (AFM) order , the low-temperature physics of this system has generally been assumed to be governed solely by AFM interactions between the dipolar and multipolar Ce moments . Here we overturn this established picture by observing an intense ferromagnetic (FM) low-energy collective mode that dominates the magnetic excitation spectrum of CeB6. Inelastic neutron-scattering data reveal that the intensity of this FM excitation significantly exceeds that of conventional spin-wave magnons emanating from the AFM wavevectors, thus placing CeB6 much closer to a FM instability than previously anticipated. This propensity for ferromagnetism may account for much of the unexplained behaviour of CeB6, and should lead to a re-examination of existing theories that have so far largely neglected the role of FM interactions.
authors.affiliation: 1] Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany [2] Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
authors.forename: Hoyoung
authors.initials: H
authors.lastname: Jang
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Friemel
authors.affiliation: Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex, France.
authors.forename: J
authors.initials: J
authors.lastname: Ollivier
authors.affiliation: I. M. Frantsevich Institute for Problems of Material Sciences of NAS, 3 Krzhyzhanovsky str. 03680 Kiev, Ukraine.
authors.forename: A V
authors.initials: AV
authors.lastname: Dukhnenko
authors.affiliation: I. M. Frantsevich Institute for Problems of Material Sciences of NAS, 3 Krzhyzhanovsky str. 03680 Kiev, Ukraine.
authors.forename: N Yu
authors.initials: NY
authors.lastname: Shitsevalova
authors.affiliation: I. M. Frantsevich Institute for Problems of Material Sciences of NAS, 3 Krzhyzhanovsky str. 03680 Kiev, Ukraine.
authors.forename: V B
authors.initials: VB
authors.lastname: Filipov
authors.affiliation: Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Keimer
authors.affiliation: 1] Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany [2] Institut für Festkörperphysik, TU Dresden, D-01069 Dresden, Germany.
authors.forename: D S
authors.initials: DS
authors.lastname: Inosov