High field neutron diffraction studies on Er-Y-La single crystals with a long period Ising spin system

1.在京都大学反应堆（KUR-ND）的现有中子衍射系统上安装了超导磁体。这个系统可以很容易地操作。高场中子衍射发现Er_<0.9>Y_<0.05>La_2<0.05>单晶在4.2K和H=-3T时，（100）方向的摆线结构基面成分消失，高场中子衍射发现Er_<0.9>Y<0.1>_La_2合金在4.2K和沿着c轴的H=0.5T时，由摆线相转变为铁磁相。在0.5T以上，所有的力矩都完全沿磁场方向排列. TbRu_2Si_2和DyRu_2Si_2是长周期伊辛自旋系统，它们的高场中子衍射给出了它们的场-温度相图。在类波分子场理论的基础上，确定了变磁相的结构并讨论了其稳定性.在自旋滑移模型的基础上讨论了Pr-Co_2Si_2和NdCo_2Si_2的一维长周期调制结构，如Ho和Er的振荡磁结构. XY三角形反铁磁体RbMnBr_3的高场中子衍射给出了从一个无公度结构到另一个无公度结构的场致相变以及高场自旋翻转相的存在。场-温度相图的粗略评估。

1. Attachment of a superconducting magnet has been made to an existing neutron diffraction system at the Kyoto University Reactor -(KUR-ND). This system can be very easily operated.2. High field neutron diffraction of Er_<0.9>Y_<0.05>La_<0.05> single crystal reveals that the basal plane component of a cycloidal structure disappears at, 4.2K and H=- 3T in tlie(100)direction.3, High field neutron diffraction finds that Er_<0.9>Y_<0.1> alloy exhibits a transition from cycloidal to ferromagnetic phase at 4.2K and at H=0.5T along the c-axis. Over 0.5T all the moments are fully arranged in the field direction.4. High field neutron diffraction of TbRu_2Si_2 and DyRu_2Si_2, which are considered to be a long period Ising spin system, yields field-temperature phase a diagram for both crystals. There are metamagnetic phases, whose structures are determined and their stability is discussed oil the basis of a wave-like molecular field theory.5. One-dimensionally long period modulated structures of similar compounds Pr-Co_2Si_2 and NdCo_2Si_2 are discussed on the basis of a spin slip model, as seen in oscillatory magnetic structures of Ho and Er.6. High field neutron diffraction on an XY triangular antiferromagnet RbMnBr_3 gives an existence of field induced phase transition from an incommensurate to another incommensurate structure and also of a spin flop phase at high fields. A field-temperature phase diagram is roughly evaluated.