Blockmon Avery L, Lee Minseong, Zhang Shengzhi, Manson Zachary E, Manson Jamie L, Zapf Vivien S, Musfeldt Janice L
Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States.
National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
Inorg Chem. 2024 Jun 24;63(25):11737-11744. doi: 10.1021/acs.inorgchem.4c01249. Epub 2024 Jun 12.
The Heisenberg antiferromagnetic chain is a canonical model for understanding many-body gaps that emerge in quantum magnets, and as a result, there has been significant work on this class of materials for much of the past century. Chiral chains, on the other hand, have received markedly less attention. [Cu(pym)(HO)]SiF·HO (pym = pyrimidine) is an = 1/2 chiral antiferromagnet with an unconventional spin gap and no long-range ordering at zero field, features that distinguish it from more conventional spin chains that host simple phase diagrams and no magnetoelectric coupling. Here, we report pulsed magnetic field electrical polarization measurements, strong magnetoelectric coupling, and extraordinary magnetic field - temperature phase diagrams for this system. In addition to three low field transitions, we find a series of phase transitions between 40 and 70 T that depend on the magnetic field direction. The observation of electric polarization in a material with a nonpolar crystal structure implies symmetry-breaking magnetic ordering that creates a polar axis - a mechanism that we discuss in terms of significant interactions between the chiral chains as well as Dzyaloshinskii-Moriya effects. Further, we find second-order magnetoelectric coupling, allowing us to deduce the magnetic point group of the highest polarization phase. These findings are in contrast to expectations for an unordered one-dimensional spin chain and reveal a significantly greater complexity of behavior in applied field.
海森堡反铁磁链是理解量子磁体中出现的多体能隙的一个典型模型，因此，在过去的大半个世纪里，针对这类材料开展了大量研究工作。另一方面，手性链受到的关注则明显较少。[Cu(pym)(HO)]SiF·HO（pym = 嘧啶）是一种自旋为1/2的手性反铁磁体，具有非常规的自旋能隙且在零场下无长程有序，这些特性使其有别于那些具有简单相图且不存在磁电耦合的更传统的自旋链。在此，我们报告了该体系的脉冲磁场电极化测量、强磁电耦合以及异常的磁场 - 温度相图。除了三个低场跃迁外，我们还发现了一系列在40至70 T之间依赖于磁场方向的相变。在具有非极性晶体结构的材料中观测到电极化意味着对称性破缺的磁有序，从而产生了一个极轴——我们从手性链之间的显著相互作用以及Dzyaloshinskii - Moriya效应的角度讨论了这一机制。此外，我们发现了二阶磁电耦合，这使我们能够推断出最高极化相的磁点群。这些发现与对无序一维自旋链的预期形成对比，并揭示了在外加磁场中行为的显著更大复杂性。
