The interplay of non-Hermitian (NH) spin dynamics in coupled ferromagnetic (FM) systems has unveiled intriguing phenomena, notably the manifestation of FM-antiferromagnetic (AFM) phase transitions at exceptional points (EPs). Extending beyond traditional FM media, ferrimagnetic (FiM) media combine the advantages of AFM and FM systems, displaying distinct attributes especially at the angular momentum composition (AMC) point, $x_{\mathrm{AMC}}$. This study explores the profound influence of FiM composition on the NH spin dynamics of a coupled FiM system. At $x_{\mathrm{AMC}}$, the spin dynamics depicted by the Néel vector demonstrates a parity-time $\left(\mathcal{PT}\right)$ symmetry, exhibiting power-law frequency splitting concerning external perturbations at the EP with a fixed power of 1/2. However, deviation from $x_{\mathrm{AMC}}$ leads to partial converging of eigenfrequency branches at the EP owing to the uncompensated angular momentum, displaying power-law frequency splitting with varied powers, akin to an effective coupled RLC circuit with capacitance influenced by frequency variations. This investigation opens a unique avenue in the area of $\mathcal{PT}$ symmetry in magnetic NH systems, unraveling the nuanced behaviors of coupled FiM configurations.

中文翻译：

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耦合亚铁磁系统中的非厄米自旋动力学

耦合铁磁 (FM) 系统中非厄米 (NH) 自旋动力学的相互作用揭示了有趣的现象，特别是异常点 (EP) 处 FM-反铁磁 (AFM) 相变的表现。亚铁磁 (FiM) 介质超越了传统的 FM 介质，结合了 AFM 和 FM 系统的优点，特别是在角动量成分 (AMC) 点上表现出独特的属性，$X_{\mathrm{航空医学中心}}$。本研究探讨了 FiM 组成对耦合 FiM 系统的 NH 自旋动力学的深远影响。在$X_{\mathrm{航空医学中心}}$，尼尔矢量描绘的自旋动力学展示了宇称时间$（\mathcal{PT}）$对称性，表现出关于 EP 的外部扰动的幂律频率分裂，固定幂为 1/2。然而，偏离$X_{\mathrm{航空医学中心}}$由于未补偿的角动量，导致 EP 处的本征频率分支部分收敛，显示出不同功率的幂律频率分裂，类似于电容受频率变化影响的有效耦合 RLC 电路。这项调查在该领域开辟了一条独特的途径$\mathcal{PT}$磁性 NH 系统中的对称性，揭示了耦合 FiM 配置的细微差别。