Magnetic Order and Spin Dynamics in Ferroelectric HoMnO3
O.P. Vajk, M. Kenzelmann, J.W. Lynn, S.B. Kim, S.-W. Cheong
Hexagonal HoMnO3 is a frustrated antiferromagnet (Tn=72 K) ferroelectric (Tc=875 K) in which these two order parameters are coupled. Our neutron measurements of the spin wave dispersion for the S=2 Mn(3+) 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 0.093 meV above the spin reorientation transition at 40 K, and 0.126 meV below. For H parallel to c the magnetic structures and phase diagram have been determined, and reveal additional transitions below 8 K where the ferroelectrically displaced Ho(3+) ions are ordered magnetically.
Name: Owen Vajk
mentor: Jeff Lynn
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NCNR, Bldg 235
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