arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2006.03425cond-mat.mtrl-scicond-mat.str-el
收藏

Cu $_3$ Nb $_2$ O $_8$中自旋密度波序的模拟

Imitation of spin density wave order in Cu$_3$Nb$_2$O$_8$

N. Giles-Donovan, N. Qureshi, R. D. Johnson, L. Y. Zhang, S. -W. Cheong, S. Cochran, C. Stock

摘要:

自旋密度波,调制本地的时刻的基础上,通常与金属材料,但最近有报道显示耦合的磁性和结构序参数的绝缘体。我们讨论了一个这样的例子,多铁性Cu $_3$ Nb $_2$ O $_8$,据报道,它经历了两个磁相变,首先到$T_N \approx 26.5K$的自旋密度波相,然后到与低于$T_2 \approx 24K$的电极化的强度耦合的螺旋结构[R. D. Johnson等人,物理学评论快报,107,137205(2011)],这打破了晶体学反转对称性。我们应用球旋光法来确认低温磁结构,但只观察到一个单一的磁相变螺旋顺序。我们认为,报告的自旋密度波起源于磁序参数的组件的去耦,允许的对称性和驱动的热波动。这为磁性而非核结构提供了破坏反转对称性的机制,从而产生中间相,其中结构模仿自旋密度波。当温度降低时,该中间结构使晶体不稳定,使得诱导结构手性,如通过电极化的强度的出现所反映的,并且仿自旋密度波弛豫成一般螺旋面。这提供了磁结构破坏反转对称而晶体结构保持中心对称的情况。

英文摘要:

Spin density waves, based on modulated local moments, are usually associated with metallic materials, but have recently been reported in insulators which display coupled magnetic and structural order parameters. We discuss one such example, the multiferroic Cu$_3$Nb$_2$O$_8$, which is reported to undergo two magnetic phase transitions, first to a spin density wave phase at $T_N \approx 26.5K$, and then to a helicoidal structure coupled to an electric polarization below $T_2 \approx 24K$ [R. D. Johnson, et al., Phys. Rev. Lett., 107, 137205 (2011)] which breaks the crystallographic inversion symmetry. We apply spherical polarimetry to confirm the low-temperature magnetic structure, yet only observe a single magnetic phase transition to helicoidal order. We argue that the reported spin density wave originates from a decoupling of the components of the magnetic order parameter, as allowed by symmetry and driven by thermal fluctuations. This provides a mechanism for the magnetic, but not nuclear, structure to break inversion symmetry thereby creating an intermediate phase where the structure imitates a spin density wave. As the temperature is reduced, this intermediate structure destabilizes the crystal such that a structural chirality is induced, as reflected by the emergence of the electric polarization, and the imitation spin density wave relaxes into a generic helicoid. This provides a situation where the magnetic structure breaks inversion symmetry while the crystal structure remains centrosymmetric.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑