探索反法拉第效应对全光螺旋依赖磁化切换的影响
Exploring the impact of the inverse Faraday effect on all-optical helicity-dependent magnetization switching
AI总结：
该研究探讨了反法拉第效应在全光螺旋依赖磁化切换中的作用，通过实验验证了磁圆二色性和反法拉第效应在磁化切换中的协同作用，揭示了电子温度与诱导磁化之间的关系。
摘要：
全光螺旋依赖磁化切换（AO-HDS）是使用仅超短激光脉冲的最快数据记录技术。FePt颗粒为研究产生磁化切换的相互作用提供了理想平台。我们确定磁圆二色性（MCD）和反法拉第效应（IFE）为主要的切换力。超快光子吸收迅速提升电子温度，使磁化淬灭。MCD的螺旋依赖吸收确保了不同的电子温度，通过在每个自旋通道中生成不同的自旋噪声率，保持有限的切换概率。IFE诱导磁矩，增强此概率。我们展示了在近红外光谱范围（800 nm至1500 nm）内使用超短激光脉冲（<200 fs）的AO-HDS实验，展示了切换效率与吸收能量密度之间的相关性。将电子温度提升到居里点使IFE能够诱导磁矩，从而在淬灭磁化状态下实现确定性切换。与薄膜或多层中由磁畴壁运动和磁畴生长主导的切换过程不同，增加纳米颗粒中的MCD不会提高切换效率。居里温度附近的电子通常会因由IFE生成的更高诱导磁化而达到更高的切换速率。MCD设定了必要的切换条件，分离电子温度。IFE生成磁矩，使自旋朝向期望方向，提高切换效率。每次激光脉冲为每个颗粒启动新的切换概率，增加由IFE提供的方向指示作用。更强的吸收确保在低切换通量下产生更高的诱导磁化。
英文摘要：
All-optical helicity-dependent magnetization switching (AO-HDS) is the quickest data recording technique using only ultrashort laser pulses. FePt grains provide an ideal platform for examining the interaction of effects conducting magnetization switching. We identify the magnetic circular dichroism (MCD) and the inverse Faraday effect (IFE) as the primary switching forces. Ultrafast photon absorption rapidly elevates electron temperatures, quenching magnetization. The MCD's helicity-dependent absorption ensures distinct electron temperatures, holding a finite switching probability by generating different spin noise rates in each spin channel. The IFE induces a magnetic moment, enhancing this probability. We present ultrashort laser pulse (<200 fs) AO-HDS experiments in the near-infrared spectral range from 800 nm to 1500 nm, demonstrating a correlation between switching efficiency and absorbed energy density. Elevating electron temperatures to the Curie point enables the IFE to induce a magnetic moment for deterministic switching in the quenched magnetization state. Unlike in films or multilayers, where domain wall motion and domain growth govern the switching process, increasing the MCD in nanometer-sized grains does not enhance switching efficiency. Electrons around the Curie temperature typically reach increased switching rates for higher induced magnetization generated by the IFE. The MCD sets the necessary switching condition, separating electron temperatures. The IFE generates a magnetic moment, directing spins toward the desired orientation and improving switching efficiency. Every laser pulse initiates a new switching probability for each grain, increasing the role of direction indication by the IFE. Stronger absorption assures higher induced magnetization at low switching fluences.
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