AI 中文总结
本研究通过多种实验与建模方法，证实α-Cu2P2O7为bc平面内二维耦合自旋二聚化反铁磁晶格，明确其交换耦合参数、能隙来源及磁相图，解决了该材料微观磁性模型的争议。
AI 中文摘要
低维量子磁体α-Cu2P2O7的微观磁性模型一直存在争议。我们利用温度依赖的非弹性中子散射、中子衍射、磁化测量以及全面的自旋波建模，对其磁性基态和激发谱开展了综合研究。我们的结果明确证实，α-Cu2P2O7是bc平面内的二维耦合自旋二聚化反铁磁（AF）晶格，其主导反铁磁交换J2 = 7.73 meV（以下称为“二聚体内交换”），二维晶格中存在较弱的交换耦合J1、J3和J4（以下称为“二聚体间交换”），这与基于LDA的密度泛函理论结果一致，与先前GGA+U的预测相反。研究发现，主导的二聚体内反铁磁交换发生在第七近邻Cu-Cu离子对之间[Cu-Cu间距d(Cu-Cu) = 5.125(3) Å]，而非结构二聚体的近邻Cu-Cu离子对之间[Cu-Cu间距d(Cu-Cu) = 3.014(1) Å]。弱层间耦合（J5 = 0.03 meV）在TN = 25 K以下稳定了长程反铁磁有序。我们进一步识别出与畸变CuO5多面体相关的弱单离子各向异性，该各向异性在自旋激发谱中打开能隙，并驱动场诱导的变磁转变。系统的自旋波计算阐明了层间耦合J5和各向异性项D在不同反铁磁区中心产生两个不同能隙的独特作用。互补的中子衍射和外加磁场依赖的磁化测量揭示了此前被忽视的13 kOe附近的变磁转变，并构建了H-T平面内的磁相图。
英文摘要
The microscopic magnetic model of the low-dimensional quantum magnet alpha-Cu2P2O7 has remained controversial. We present a comprehensive study of its magnetic ground state and excitation spectrum using temperature-dependent inelastic neutron scattering, neutron diffraction, magnetization measurements, and comprehensive spin-wave modeling. Our results unambiguously establish alpha-Cu2P2O7 as a two-dimensionally coupled spin-dimerized antiferromagnetic (AF) lattice within the bc plane, with a dominant AF exchange J2 = 7.73 meV (hereafter referred to as "intradimer exchange") and weaker exchange couplings J1, J3, and J4 in the two-dimensional lattice (hereafter referred to as "interdimer exchange"), in agreement with LDA-based density functional theory and in contrast to previous GGA+U predictions. The dominant intradimer AF exchange is found between seventh-nearest-neighbor Cu-Cu ion pairs [d(Cu-Cu) = 5.125(3) A] rather than nearest-neighbor Cu-Cu ion pairs [d(Cu-Cu) = 3.014(1) A] of the structural dimers. Weak interlayer coupling (J5 = 0.03 meV) stabilizes long-range antiferromagnetic order below TN = 25 K. We further identify a weak single-ion anisotropy, associated with the distorted CuO5 polyhedra, that opens a gap in the spin-excitation spectrum and drives a field-induced metamagnetic transition. Systematic spin-wave calculations elucidate the distinct roles of interlayer coupling J5 and anisotropy term D in producing two distinct energy gaps at different antiferromagnetic zone centers. Complementary neutron diffraction and magnetization measurements as a function of applied magnetic field uncover a previously overlooked metamagnetic transition near 13 kOe and allow construction of the magnetic phase diagram in the H-T plane.
Comments45 pages, 14 Figures, 5 Tables
Journal refPhys. Rev. B 114, 094412 (2026)
