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首页> 外文期刊>Physical review >Magnetic phase transitions and spin density distribution in the molecular multiferroic system GaV_4S_8
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Magnetic phase transitions and spin density distribution in the molecular multiferroic system GaV_4S_8

机译：分子多体系统中的磁相转变和旋转密度分布Gav_4s_8

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We have carried out neutron diffraction and small-angle neutron scattering measurements on a high-quality single crystal of the cubic lacunar spinel multiferroic, GaV_4S_8, as a function of magnetic field and temperature to determine the magnetic properties for the single electron that is located on the tetrahedrally coordinated V_4 molecular unit. Our results are in good agreement with the structural transition at 44 K from cubic to rhombohedral symmetry where the system becomes a robust ferroelectric, while long-range magnetic order develops below 13 K in the form of an incommensurate cycloidal magnetic structure, which can transform into a Neel-type skyrmion phase in a modest applied magnetic field. Below 5.9(3) K, the crystal enters a ferromagnetic phase, and we find the magnetic order parameter indicates a long-range-ordered ground state with an ordered moment of 0.23(1) μ_B per Ⅴ ion. Both polarized and unpolarized neutron data in the ferroelectric-paramagnetic phase have been measured to determine the magnetic form factor. The data are consistent with a model of the single spin being uniformly distributed across the V_4 molecular unit, rather than residing on the single apical Ⅴ ion, in substantial agreement with the results of first-principles theory. In the magnetically ordered state, polarized neutron measurements are important since both the cycloidal and ferromagnetic order parameters are clearly coupled to the ferroelectricity, causing the structural peaks to be temperature and field dependent. For the ferromagnetic ground state, the spins are locked along the [1,1,1] direction by a surprisingly large anisotropy.
机译：我们已经在立方曲面型尖晶石多体型，GAV_4S_8的高质量单晶上进行了中子衍射和小角中子散射测量，作为磁场和温度的函数，以确定位于的单个电子的磁性四面体协调的V_4分子单元。我们的结果与从立方体到菱形对称的结构过渡，系统变为强大的铁电，而长范围磁场以不称称的环形磁性结构的形式显影，可以转化为13 k一种适度应用磁场中的Neel型次幂阶段。下面5.9（3）k，晶体进入铁磁相，我们发现磁性订单参数表示长距离有序的接地状态，每ⅴ离子0.23（1）μ_b的有序时刻。已经测量了铁电调节阶段的偏振和非极化中子数据，以确定磁性形状因子。数据与均匀分布在V_4分子单元上的单个旋转的模型一致，而不是驻留在单个顶端ⅴ离子上，与第一原则理论的结果相当大。在磁性有序状态下，极化中子测量值很重要，因为条环形和铁磁阶参数都清楚地耦合到铁电性，使结构峰值是温度和场的依赖性。对于铁磁接地状态，旋转沿着[1,1,1]方向锁定，令人惊讶的大部分各向异性。

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  • 来源
    《Physical review》 |2020年第1期|014410.1-014410.10|共10页
  • 作者

    Rebecca L. Dally; William D. Ratcliff Ⅱ; Lunyong Zhang; Heung-Sik Kim; Markus Bleuel; J. W. Kim; Kristjan Haule; David Vanderbilt; Sang-Wook Cheong; Jeffrey W. Lynn;

  • 作者单位

    NIST Center for Neutron Research National Institute of Standards and Technology Gaithersburg Maryland 20899-6102 USA;

    NIST Center for Neutron Research National Institute of Standards and Technology Gaithersburg Maryland 20899-6102 USA Department of Materials Science and Engineering University of Maryland College Park Maryland 20742 USA;

    Laboratory for Pohang Emergent Materials Pohang Accelerator Laboratory and Max Plank POSTECH Center for Complex Phase Materials Pohang University of Science and Technology Pohang 790-784 Korea School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China;

    Department of Physics Kangwon National University Chuncheon 24341 Republic of Korea Department of Physics and Astronomy Rutgers University Piscataway New Jersey 08854 USA;

    NIST Center for Neutron Research National Institute of Standards and Technology Gaithersburg Maryland 20899-6102 USA Department of Materials Science and Engineering University of Maryland College Park Maryland 20742 USA;

    Department of Physics and Astronomy Rutgers University Piscataway New Jersey 08854 USA Rutgers Center for Emergent Materials Rutgers University Piscataway New Jersey 08854 USA;

    Department of Physics and Astronomy Rutgers University Piscataway New Jersey 08854 USA;

    Department of Physics and Astronomy Rutgers University Piscataway New Jersey 08854 USA;

    Laboratory for Pohang Emergent Materials Pohang Accelerator Laboratory and Max Plank POSTECH Center for Complex Phase Materials Pohang University of Science and Technology Pohang 790-784 Korea Department of Physics and Astronomy Rutgers University Piscataway New Jersey 08854 USA Rutgers Center for Emergent Materials Rutgers University Piscataway New Jersey 08854 USA;

    NIST Center for Neutron Research National Institute of Standards and Technology Gaithersburg Maryland 20899-6102 USA;

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