title: Magnetic order and spin dynamics in ferroelectric HoMnO3.
abstract: Hexagonal HoMnO3 is a frustrated antiferromagnet (T(N)=72 K) ferroelectric (T(C)=875 K) in which these two order parameters are coupled. Our neutron measurements of the spin-wave dispersion for the S=2 Mn3+ on the layered triangular lattice are well described by a two-dimensional nearest-neighbor Heisenberg exchange J=2.44 meV, and an anisotropy D that is 0.28 meV above the spin-reorientation transition at 40 K and 0.38 meV below. For H parallel c the magnetic structures and phase diagram have been determined, and reveal additional transitions below 8 K where the ferroelectrically displaced Ho3+ ions are ordered magnetically.
authors.affiliation: Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
authors.forename: O P
authors.initials: OP
authors.lastname: Vajk
authors.forename: M
authors.initials: M
authors.lastname: Kenzelmann
authors.forename: J W
authors.initials: JW
authors.lastname: Lynn
authors.forename: S B
authors.initials: SB
authors.lastname: Kim
authors.forename: S-W
authors.initials: SW
authors.lastname: Cheong