Magnetic Structure and Quadrupolar Order Parameter Driven by Geometrical Frustration Effect in NdB4
Magnetic Structure and Quadrupolar Order Parameter Driven by Geometrical Frustration Effect in NdB4
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DOI：
10.7566/jpsj.86.044705
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发表时间：
2017-04-15
影响因子：
1.7
通讯作者：
Fernandez-Baca, Jaime A.
中科院分区：
文献类型：
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作者：
Yamauchi, Hiroki;Metoki, Naoto;Fernandez-Baca, Jaime A.
利用中子衍射实验研究了NdB_4中间相的磁结构和序参量，该中间相在T-0 = 17.2K、T-N_1 = 7.0K和T-N_2 = 4.8K发生了连续相变。我们揭示了传播矢量为q（0）=（0，0，0），q（0）和q（s1）=（0，0，0）的反铁磁有序（delta，delta，0.4）（delta类似于0.14），以及q（0）和q（s2）=（0.2，0，0.4）分别在阶段II（T-N1 < T < T-0）、阶段III（T-N2 < T < T-N1）和阶段IV（T < T-N2）中。在第二阶段中观察到的图案成功地解释了通过假设一个共面结构的静磁矩在tetraxab平面。我们发现，第II相的磁结构可以被唯一地确定为反铁磁“全进/全出”型（Gamma（4））和“涡旋”型（Gamma（2））结构的线性组合，由Gamma（4）主分量（77%）和小振幅的Gamma（2）（23%）组成。我们认为四极相互作用是稳定非共线磁结构和四极有序的关键。在这里，Shastry-Sutherland晶格中的挫折将在抑制磁相互作用的主导方面发挥重要作用。
Neutron diffraction experiments have been carried out to characterize the magnetic structures and order parameters in an intermediate phase of NdB4 showing the successive phase transitions at T-0 = 17.2 K, T-N1 = 7.0 K, and T-N2 = 4.8 K. We have revealed the antiferromagnetic ordering with the propagation vectors q(0) = (0, 0, 0), q(0) and q(s1) = (delta, delta, 0.4) (delta similar to 0.14), and q(0) and q(s2) = (0.2, 0,0.4) in phase II (T-N1 < T < T-0), phase III (T-N2 < T < T-N1), and phase IV (T < T-N2), respectively. The observed patterns in phase II are successfully explained by postulating a coplanar structure with static magnetic moments in the tetragonal ab-plane. We have found that the magnetic structure in phase II can be uniquely determined to be a linear combination of antiferromagnetic "all-in/all-out"-type (Gamma(4)) and "vortex"-type (Gamma(2)) structures, consisting of a Gamma(4) main component (77%) with a small amplitude of Gamma(2) (23%). We propose that the quadrupolar interaction holds the key to stabilizing the noncollinear magnetic structure and quadrupolar order. Here, the frustration in the Shastry-Sutherland lattice would play an essential role in suppressing the dominance of the magnetic interaction.