CoFeB纳米带中自旋波驱动横向畴壁移动动力学研究

Dynamics of transverse domain wall movement in CoFeBnanostrips driven by spin waves

CoFeB具有较大的饱和磁化强度和较低的阻尼系数,适合制备可控畴壁移动器件。通过微磁模拟,探究CoFeB纳米带中自旋波与横向畴壁间的动力学相互作用。模拟结果表明畴壁移动的速度和方向不仅受到自旋波频率的影响,而且和外加磁场强度、纳米带宽度等参数密切相关。当自旋波频率较低时畴壁难以被驱动,随着自旋波频率的升高,畴壁开始移动且移动方向与自旋波的传播方向相反。随着外加磁场强度的增大,畴壁反向移动速度先增大后减小,直至变为正向移动。当自旋波频率高于7 GHz时,畴壁的移动方向与自旋波的传播方向相同,并且畴壁速度随自旋波频率的变化呈现多峰结构,最大速度为384 m/s。畴壁正向移动时,其速度随外加磁场强度的增加逐渐变大。当纳米带的宽度增加时,畴壁有效场的不均匀性和质量都会增大,使畴壁移动的最大速度先增大后减小。使用CoFeB纳米带可以有效提高畴壁的移动速度,并且外加磁场强度与纳米带宽度对畴壁速度有显著的影响,为优化器件性能提供了新思路。

CoFeB has the large saturation magnetization and low damping constant,which makes it a suitable material to fabricate the memory devices by controlling domain wall moving.In this paper,we investigate the kinetic interactions between spin waves and transverse domain walls in CoFeB nanostrips by means of micromagnetic simulations.The simulation results show that the speed and direction of domain wall movement are not only influenced by the spin wave frequency,but also closely related to the applied magnetic field strength and nanostrip s width.When the spin wave frequency is low,the domain wall is difficult to be driven.As the spin wave frequency increases,the domain wall starts to move in the direction opposite to the propagation of the spin wave.With the increase of the strength of the applied magnetic field,the velocity of the domain wall moving in the reverse direction increases and then decreases until it becomes forward.When the spin wave frequency is higher than 7 GHz,the domain wall moves in the same direction as the spin wave propagation,and the velocity of the domain wall shows a multi-peak feature with the spin wave frequency,with the maximum velocity obtained to be 384 m/s.When the domain wall moves forward,its velocity gradually increases with the increase of the strength of the applied magnetic field.As the width of the nanostrip increases,both the mass of the domain wall and the inhomogeneity of the effective field increase,causing the maximum velocity of the domain wall to increase and then decrease.The use of CoFeB nanostrips can effectively improve the domain wall velocity,and the strength of the applied magnetic field and the width of the nanostrip have a significant effect on the domain wall velocity,which provides a new way to optimize the device performance.