Elastically induced magnetization at ultrafast time scales in a chiral helimagnet
Elastically induced magnetization at ultrafast time scales in a chiral helimagnet
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DOI：
10.1103/physrevb.106.035103
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发表时间：
2022-07
影响因子：
3.7
通讯作者：
Hengzhou Liu;M. Trinh;E. M. Clements;D. Sapkota;Ling Li;Zachary Romestan;S. Bhat;V. Mapara;A. Barua;Samuel Langelund Carrera;M. Phan;D. Arena;H. Srikanth;D. Mandrus;A. Romero;D. Karaiskaj
中科院分区：
文献类型：
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作者：
Hengzhou Liu;M. Trinh;E. M. Clements;D. Sapkota;Ling Li;Zachary Romestan;S. Bhat;V. Mapara;A. Barua;Samuel Langelund Carrera;M. Phan;D. Arena;H. Srikanth;D. Mandrus;A. Romero;D. Karaiskaj
手征螺旋磁材料由于具有长程螺旋磁序、拓扑自旋织构和潜在的Skyrmion等特性，近年来在自旋电子学领域引起了广泛的关注。如果超快磁存储器可以被超快光脉冲控制，那么它们的强自旋织构将提供一种新的超快磁存储概念。利用时间分辨的磁光克尔谱，我们证明了超快光脉冲可以在单晶手征螺旋磁体中产生磁性。在低温和磁场的情况下，表现出一个手性螺旋磁相与长程螺旋自旋秩序，但它包含零净磁化。然而，在激光脉冲激发后，我们观察到磁化形成超过几十皮秒，远远超过激光脉冲的持续时间。我们将这种奇特的行为归因于激光诱导的相变，从手性helmagnetic阶段，零净磁化，到一个手性圆锥helmagnetic阶段，有限的magnetization.Ab initiodensityfunctionalcalculation提供了一个详细的微观图片背后的观察机制。共振磁振子声子耦合特定的声子导致的手征螺旋磁相的弹性变形。最后，在有限的磁场中，净磁化强度被激光脉冲激发并在平衡位置附近进动，导致作为特定磁相位处的外部磁场的函数的异常磁化进动。
Chiral helimagnetic materials have recently attracted much attention for spintronic applications due to their long-range helical magnetic order, topological spin textures, and potential for hosting skyrmions. Their robust spin texture would provide a new concept of ultrafast magnetic memory if it can be controlled by an ultrafast optical pulse. Using time-resolved magneto-optical Kerr spectroscopy, we show that magnetism in the single-crystalline chiral helimagnetcan be induced by an ultrafast optical pulse. At low temperatures and in the absence of magnetic fields,exhibits a chiral helical magnetic phase with a long-range helical spin order, but it contains zero net magnetization. However, after the laser pulse excitation we observe magnetization forming over tens of picoseconds, far exceeding the duration of the laser pulse. We attribute this peculiar behavior to a laser-induced phase transition from the chiral helimagnetic phase, with zero net magnetization, to a chiral conical helimagnetic phase, with finite magnetization.Ab initiodensity functional calculations provide a detailed microscopic picture of the mechanism behind the observation. The resonant magnon-phonon coupling with specific phonons leads to an elastic deformation of the chiral helimagnetic phase. Finally, at finite magnetic fields, the net magnetization is excited by the laser pulse and precesses around the equilibrium position, leading to anomalous magnetization precession as a function of the external magnetic field at specific magnetic phases.