Fast Switching of Mesoscopic Magnets
Fast Switching of Mesoscopic Magnets
复制标题
介观磁体的快速切换
DOI：
--
复制
发表时间：
2003
期刊：
影响因子：
--
通讯作者：
Hermann Forster Vienna
中科院分区：
文献类型：
--
作者：
T. Schrefl;J. Fidler;R. Dittrich;D. Suess;W. Scholz;V. Tsiantos;Hermann Forster Vienna
亚微米大小的磁体的开关时间大约在皮秒到纳秒之间。开关速度由磁体的几何形状、固有磁性能以及外加磁场的方向和强度控制。岁差运动支配着小磁性粒子的开关动力学。如果外场的上升时间快于磁化向最近的局部最小值的弛豫，则在各向异性场以下的场中可以实现粒子的快速切换。薄膜元件的开关速度取决于反转模式。发现了两种不同的反转模式：(1)反畴的成核和扩展；(2)磁化的非均匀旋转。畴形核发生在随机取向的粒状hcp-Co薄膜和垂直各向异性的粒状CoCrPt元素中。在颗粒状fcc-Co薄膜中发现了旋转过程。旋转的开关比成核和扩展的开关快四倍。旋转开关可以通过施加足够大的旋转场来实现。热激活减少开关时间。
The switching times of submicron-sized magnets are of the order of pico-to nanoseconds. The switching speed is controlled by the geometric shape of the magnets, the intrinsic magnetic properties, and the orientation and strength of the applied field. Precessional motion governs the switching dynamics of small magnetic particles. If the rise time of the external field is faster than the relaxation of the magnetization toward the nearest local minimum, fast switching of particles is possible in fields below the anisotropy field. The switching speed of thin-film elements depends on the reversal mode. Two distinct reversal modes are found: (1) nucleation and expansion of reversed domains and (2) nonuniform rotation of the magnetization. Domain nucleation occurs in randomly oriented, granular hcp-Co thin films and granular CoCrPt elements with perpendicular anisotropy. Rotational processes are found in granular fcc-Co thin films. The switching by rotation is about four times faster than switching by nucleation and expansion of domains. Switching by rotation can be enforced by applying a sufficiently large rotational field. Thermal activation decreases switching time.