Vajk O P, Kenzelmann M, Lynn J W, Kim S B, Cheong S-W
Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Phys Rev Lett. 2005 Mar 4;94(8):087601. doi: 10.1103/PhysRevLett.94.087601.
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.
六方 HoMnO₃ 是一种受挫反铁磁体（奈尔温度 T(N)=72 K）和铁电体（居里温度 T(C)=875 K），其中这两个序参量相互耦合。我们对层状三角晶格上 S=2 的 Mn³⁺ 的自旋波色散进行的中子测量，很好地符合二维最近邻海森堡交换 J=2.44 毫电子伏特，以及在 40 K 时自旋重取向转变之上为 0.28 毫电子伏特、之下为 0.38 毫电子伏特的各向异性 D。对于磁场 H 平行于 c 轴的情况，已经确定了磁结构和相图，并且揭示了在 8 K 以下存在额外的转变，此时发生铁电位移的 Ho³⁺ 离子会发生磁有序排列。
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