Oyeka Ebube E, Winiarski Michał J, Sorolla Ii Maurice, Taddei Keith M, Scheie Allen, Tran Thao T
Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States.
Faculty of Applied Physics and Mathematics and Advanced Materials Center, Gdansk University of Technology, ul. Narutowicza 11/12, 80-233 Gdansk, Poland.
Inorg Chem. 2021 Nov 1;60(21):16544-16557. doi: 10.1021/acs.inorgchem.1c02432. Epub 2021 Oct 12.
Magnetic polar materials feature an astonishing range of physical properties, such as magnetoelectric coupling, chiral spin textures, and related new spin topology physics. This is primarily attributable to their lack of space inversion symmetry in conjunction with unpaired electrons, potentially facilitating an asymmetric Dzyaloshinskii-Moriya (DM) exchange interaction supported by spin-orbital and electron-lattice coupling. However, engineering the appropriate ensemble of coupled degrees of freedom necessary for enhanced DM exchange has remained elusive for polar magnets. Here, we study how spin and orbital components influence the capability of promoting the magnetic interaction by studying two magnetic polar materials, α-Cu(IO) (D) and Mn(IO) (S), and connecting their electronic and magnetic properties with their structures. The chemically controlled low-temperature synthesis of these complexes resulted in pure polycrystalline samples, providing a viable pathway to prepare bulk forms of transition-metal iodates. Rietveld refinements of the powder synchrotron X-ray diffraction data reveal that these materials exhibit different crystal structures but crystallize in the same polar and chiral 2 space group, giving rise to an electric polarization along the -axis direction. The presence and absence of an evident phase transition to a possible topologically distinct state observed in α-Cu(IO) and Mn(IO), respectively, imply the important role of spin-orbit coupling. Neutron diffraction experiments reveal helpful insights into the magnetic ground state of these materials. While the long-wavelength incommensurability of α-Cu(IO) is in harmony with sizable asymmetric DM interaction and low dimensionality of the electronic structure, the commensurate stripe AFM ground state of Mn(IO) is attributed to negligible DM exchange and isotropic orbital overlapping. The work demonstrates connections between combined spin and orbital effects, magnetic coupling dimensionality, and DM exchange, providing a worthwhile approach for tuning asymmetric interaction, which promotes evolution of topologically distinct spin phases.
磁性极性材料具有一系列惊人的物理特性，如磁电耦合、手性自旋纹理以及相关的新自旋拓扑物理学。这主要归因于它们缺乏空间反演对称性以及存在未成对电子，这有可能促进由自旋轨道和电子晶格耦合支持的不对称Dzyaloshinskii-Moriya（DM）交换相互作用。然而，对于极性磁体来说，设计增强DM交换所需的适当耦合自由度组合仍然难以实现。在这里，我们通过研究两种磁性极性材料α-Cu(IO)（D）和Mn(IO)（S），并将它们的电子和磁性特性与其结构联系起来，研究自旋和轨道分量如何影响促进磁相互作用的能力。这些配合物的化学控制低温合成得到了纯多晶样品，为制备块状过渡金属碘酸盐提供了一条可行的途径。粉末同步加速器X射线衍射数据的Rietveld精修表明，这些材料表现出不同的晶体结构，但结晶于相同的极性和手性2空间群，沿轴方向产生极化。分别在α-Cu(IO)和Mn(IO)中观察到的向可能的拓扑不同状态的明显相变的存在和不存在，暗示了自旋轨道耦合的重要作用。中子衍射实验揭示了对这些材料磁基态的有益见解。虽然α-Cu(IO)的长波长不可公度性与相当大的不对称DM相互作用和电子结构的低维性相一致，但Mn(IO)的相称条纹反铁磁基态归因于可忽略不计的DM交换和各向同性的轨道重叠。这项工作展示了自旋和轨道联合效应、磁耦合维度和DM交换之间的联系，为调节不对称相互作用提供了一种有价值的方法，这种相互作用促进了拓扑不同自旋相的演化。
