field-dependent XFMR fitting

Co-edge XFMR amplitude-vs-field and phase-vs-field data sets; MATLAB code for fitting (example: fit results shown in Fig. 4 in 10.1021/acs.nanolett.0c01868)<br>Abstract of the associated publication (10.1021/acs.nanolett.0c01868) - Spin currents can exert spin-transfer torques on magnetic systems even in the limit of vanishingly small net magnetization, as recently shown for antiferromagnets. Here, we experimentally show that a spin-transfer torque is operative in a macroscopic ensemble of weakly interacting, randomly magnetized Co nanomagnets. We employ element- and time-resolved X-ray ferromagnetic resonance (XFMR) spectroscopy to directly detect subnanosecond dynamics of the Co nanomagnets, excited into precession with cone angle ≳0.003° by an oscillating spin current. XFMR measurements reveal that as the net moment of the ensemble decreases, the strength of the spin-transfer torque increases relative to those of magnetic field torques. Our findings point to spin-transfer torque as an effective way to manipulate the state of nanomagnet ensembles at subnanosecond time scales.

钴边X射线铁磁共振（Co-edge X-ray Ferromagnetic Resonance, Co-edge XFMR）的振幅-磁场关系与相位-磁场关系数据集；用于参数拟合的MATLAB代码（拟合结果示例见文献10.1021/acs.nanolett.0c01868的图4）
相关出版物（DOI: 10.1021/acs.nanolett.0c01868）的摘要：自旋流可在净磁化强度近乎为零的极限条件下对磁系统施加自旋转移扭矩（spin-transfer torque），正如近期针对反铁磁体的研究所证实的那样。本研究通过实验证明，在弱相互作用、随机磁化的钴纳米磁体宏观集合体中，自旋转移扭矩可有效发挥作用。我们采用元素分辨与时间分辨X射线铁磁共振（X-ray Ferromagnetic Resonance, XFMR）光谱技术，直接探测钴纳米磁体的亚纳秒级动力学行为：该动力学过程由振荡自旋流激发为进动状态，进动锥角≳0.003°。X射线铁磁共振测量结果显示，随着该集合体的净磁矩降低，自旋转移扭矩的强度相较于磁场扭矩的强度显著提升。本研究结果表明，自旋转移扭矩是在亚纳秒时间尺度上调控纳米磁体集合体态的有效手段。