Magnetic order and spin dynamics in ferroelectric HoMnO3.
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.
Vajk
O P
OP
Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Kenzelmann
M
M
Lynn
J W
JW
Kim
S B
SB
Cheong
S-W
SW