磁热噪音下纳米铁磁线磁畴壁脱钉行为

Depinning behaviors of magnetic domain wall in ferromagnetic nanowires under magnetic thermal noise

为了考察由热起伏引起的磁性噪音(磁热噪音)对纳米铁磁线磁畴壁动力学的影响,通过微磁学模拟研究了在不同温度磁热噪音下纳米铁磁线磁畴壁脱钉(depinning)行为.为了分析磁畴壁的钉扎和脱钉行为,在纳米铁磁线上制作了一个纳米凹槽使磁畴壁牢牢地钉扎(pinning)在凹槽中.在外磁场驱动下,利用纳米铁磁线的纳米凹槽考察了磁畴壁的钉扎和脱钉行为.结果表明,在无磁热噪音条件(T=0 K)下,磁畴壁在不同纳米凹槽中受到"U"或"W"字形状能量势阱的约束,影响了磁畴壁的钉扎状态和脱钉行为.在磁热噪音条件(T≠0 K)下,纳米铁磁线磁畴壁虽然保持着自旋结构上的特征和动力学上的行为特性,但是随着温度升高,磁热噪音对纳米凹槽能量势阱的影响明显增强,不仅纳米凹槽的能量势阱形状发生变化,而且磁畴壁在纳米凹槽中的脱钉磁场强度也发生改变.这意味着在磁热噪音下利用纳米线的几何形状不易有效调控磁畴壁的动力学行为.

In order to observe the influence of the magnetic thermal noise on the magnetic domain wall dynamics in ferromagnetic nanowires, we investigated the pining and the depinning behaviors of the magnetic domain wall in the notched ferromagnetic nanowire under different temperature conditions by means of micromagnetic simulations. By the external magnetic field driving, we observed the pinning and the depinning behaviors of the domain wall in the notched ferromagnetic nanowire. Without the magnetic thermal noise T = 0 K）, due to the constraint of U-type or W-type energy potential wells in the ferromagnetic notch, the magnetic domain wall pinning state and depinning behaviors were affected. In the condition of magnetic thermal noise （T ≠ 0 K）, the influence of the magnetic thermal noise on the magnetic potential well was obviously increased with the rise of temperature, however the dynamic properties of the domain wall in the ferromagnetic nanowire was still kept. The results mean that dynamic behaviors of the magnetic domain wall are not effectively controlled by the geometry of the ferromagnetic nanowire under the magnetic thermal noise condition.