发表机构
Istituto Italiano di Tecnologia; Institute for Molecules and Materials, Radboud University（意大利理工学院; 拉德堡德大学分子与材料研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究发现交换耦合对离子位移的导数是预测绝缘反铁磁体退磁速度的可计算参数，通过实验与模拟揭示Cr₂O₃退磁远快于FeBO₃源于交换收缩效应，为相关材料筛选提供了实用路径。
AI 中文摘要
反铁磁体结合了太赫兹自旋动力学与对杂散场的不敏感性，其序参量的操控速度决定了器件的运行速度极限。飞秒光脉冲可在皮秒到纳秒的时间尺度内使不同化合物的反铁磁绝缘体退磁，目前尚无材料参数能解释该时间尺度的差异或预测新化合物的对应值。在补偿型反铁磁体中，无需角动量离开自旋系统，因此退磁速率由晶格向自旋的能量流决定。时间分辨二次谐波产生实验显示，Cr₂O₃在晶格被驱动至奈尔温度以上后，可在2皮秒内完成退磁，其速度是结构相似的FeBO₃的100倍。第一性原理计算将该差异归因于交换收缩：短Cr-Cr接触使交换耦合对原子位移的敏感性提升10倍，并扩大了声子衰变为磁振子对的相空间。采用从头算参数的自旋-晶格模拟重现了测量比值的数量级。因此，交换耦合对离子位移的导数成为可计算参数，用于预测绝缘反铁磁体的退磁速度。该结果加深了对绝缘反铁磁体超快操控的理解，并为合成前筛选热辅助反铁磁存储器的候选材料提供了实用途径。
英文摘要
Antiferromagnets combine terahertz spin dynamics with insensitivity to stray fields, and how quickly their order can be manipulated sets the speed limit on device operation. Femtosecond optical pulses demagnetize antiferromagnetic insulators on timescales that span picoseconds to nanoseconds across compounds, and no material parameter is known that accounts for the spread or predicts where a new compound will fall. In a compensated antiferromagnet, no angular momentum needs to leave the spin system, so the rate is set by energy flow from the lattice into the spins. Time-resolved second-harmonic generation experiments show that Cr2O3 demagnetizes within 2 ps once the lattice is driven above the Neel temperature, two orders of magnitude faster than the structurally similar FeBO3. First-principles calculations trace the disparity to exchange striction: short Cr-Cr contacts make the exchange coupling tenfold more sensitive to atomic displacements and widen the phase space for phonon decay into magnon pairs. Spin-lattice simulations with ab initio parameters reproduce the order of magnitude of the measured ratio. The derivative of the exchange coupling with respect to the ionic displacement thus emerges as a computable parameter that predicts how fast an insulating antiferromagnet can be demagnetized. The results advance our understanding of ultrafast control in insulating antiferromagnets, and suggest a practical pathway to screen candidate materials for thermally assisted antiferromagnetic memory before synthesis.
