Yen Peter Tsung-Wen, Wu Hung-Cheng, Huang Shin-Ming
Physics Department, National Sun Yat-sen University, Kaohsiung 80424, Taiwan.
Center for Crystal Researches, National Sun Yat-sen University, Kaohsiung 80424, Taiwan.
J Phys Condens Matter. 2022 Jun 17;34(33). doi: 10.1088/1361-648X/ac75a2.
Recently, the discovery of multiferroicity in pyrochlore-like compound CuOClhas generated significant interest, and several studies have been performed in this area. This transition metal oxychloride is unique because the divalent copper atoms create anS=1/2correlated insulator and the pyrochlore lattice tends to frustrate spins. From neutron powder diffraction measurements, an incommensurate magnetic order of the ordering vectorq=(0.827,0,0)emerges below the Néel temperature of 70 K. At this temperature or slightly above, ferroelectricity (FE) or antiferroelectricity, accompanying a lattice distortion, has been observed. Experimentally, some discrepancies remain. In this paper, we report our first-principles simulation results by evaluating the possible lattice and spin spiral states. We found that thestructure is not more stable thanFdd2(a), which is supported by our reexamination of the x-ray diffraction data. In addition, we find that after we include magnetism in the calculation, it predicts that theFdd2(a)lattice with a helical (proper screw) spin structure is energetically more stable than other spin configurations. Our results indicate charge-order-driven FE that subsequently induces magnetism.
最近，类烧绿石化合物CuOCl中多铁性的发现引起了广泛关注，并且在该领域已经开展了多项研究。这种过渡金属氯氧化物很独特，因为二价铜原子形成了一个S = 1/2的关联绝缘体，并且烧绿石晶格倾向于使自旋受挫。从中子粉末衍射测量结果来看，在70 K的奈尔温度以下出现了有序矢量q =(0.827, 0, 0)的非公度磁序。在这个温度或略高于此温度时，伴随着晶格畸变，已经观察到了铁电性（FE）或反铁电性。在实验上，仍然存在一些差异。在本文中，我们通过评估可能的晶格和自旋螺旋态来报告我们的第一性原理模拟结果。我们发现该结构并不比Fdd2(a)更稳定，这一点得到了我们对X射线衍射数据重新审视的支持。此外，我们发现在计算中考虑磁性后，它预测具有螺旋（正螺旋）自旋结构的Fdd2(a)晶格在能量上比其他自旋构型更稳定。我们的结果表明电荷有序驱动的铁电性随后会诱导磁性。
