钇铁石榴石自旋波导管中磁钉扎对自旋波模的影响

doi:10.19596/j.cnki.1001-246x.8608

摘要/Abstract

摘要：

利用微磁模拟，研究钇铁石榴石自旋波导管边界的磁钉扎对其中自旋波动力学的影响。模拟结果表明: 磁钉扎引起的双磁子散射将自旋波散射到多个方向，使得自旋波在k空间的分布更加分散。自旋波模的演化表明: 不同自旋波模的共振场不同，而双磁子散射使得自旋波模的共振场更为接近。另外，双磁子散射通过改变自旋波模的弛豫速率，改变了自旋波模的共振强度，幅度可达40%。增大自旋波导能够降低磁钉扎的影响，可以用来提升自旋波导的性能。

关键词: 双磁子散射, 自旋波导管, 磁子学, 微磁模拟

Abstract:

The effect of magnetization pinning at corners on spin wave dynamics in a spin wave conduit of yttrium iron garnet is investigated by using micromagnetic simulation. The simulation results reveal that two-magnon scattering brought on by this magnetization pinning scatters spin waves in various directions, resulting in a more dispersed spin wave pattern in k space. The evolution patterns of spin waves suggest that spin waves modes resonate at different applied magnetic fields, and magnetization pinning-induced magnon scattering brings the resonance fields of spin wave modes closer together. In addition, this magnon scattering modifies the intensity of spin wave modes at resonance, by more than 40 percent, for example, though altering their relaxation rate. By lengthening spin wave conduits the effects of this magnetization pinning could be limited, which may improve the performance of spin wave conduits.

Key words: two-magnon scattering, spin wave conduit, magnonics, micromagnetic simulation

乔士柱, 王晓波, 杨国全. 钇铁石榴石自旋波导管中磁钉扎对自旋波模的影响[J]. 计算物理, 2023, 40(4): 443-452.

Shizhu QIAO, Xiaobo WANG, Guoquan YANG. Effect of Magnetization Pinning on Spin Wave Modes in Spin Wave Conduit of Yttrium Iron Garnet[J]. Chinese Journal of Computational Physics, 2023, 40(4): 443-452.

图/表 8

Fig.1 Geometry of YIG spin wave conduit used in a micromagnetic simulation

图1 微磁模拟中使用的YIG自旋波导示意图

Fig.2 Distribution of spin waves throughout k space in (a) logarithmic z scale and (b) linear z scale

图2 自旋波在k空间的分布(a) z轴为对数坐标；(b) z轴为线性坐标

Fig.3 my distribution (a) across the YIG conduit and (b) under periodical boundary conditions

图3 my的分布(a) YIG自旋波导；(b)周期性边界条件

Fig.4 (a) Spin wave pattern under periodical boundary conditions along both the y and z directions; (b) intensity of spin wave modes with ky = 0 and fast Fourier transformation of microwave field across YIG conduit

图4 (a) y和z方向都使用周期性边界条件时自旋波在k空间的分布图; (b) ky = 0的自旋波的强度、微波场在整个YIG波导区域上的快速傅里叶变换强度分布

Fig.5 (a) Spin wave pattern when periodical boundary condition is only along the y direction; (b) intensity of spin wave modes with ky = 0 in this circumstance; (c) spin wave pattern when periodical boundary condition is only along the z direction; (d) spin wave modes intensity with ky = ny·2π/Ly, ny = 0, 1, …, 4, in this circumstance (Insert in (b) illustrates spin wave modes intensity with ky = ny·2π/Ly, ny = 0, 1, …, 4, when no periodical boundary condition is applied.)

图5 (a)周期性边界条件只沿y方向时自旋波在k空间的分布; (b) ky = 0的自旋波的强度; (c) 周期性边界条件只沿z方向时自旋波在k空间的分布; (d) ky = ny·2π/Ly，ny = 0，1，…，4的自旋波的强度((b)中的插图表示不使用周期性边界条件时ky = ny·2π/Ly，ny = 0，1，…，4的自旋波的强度。)

Fig.6 Evolution of eight spin wave modes with kz = nz·2π/Lz, nz = 0, 1, …, 7, and ky = 0, when periodical boundary conditions applied on both y and z directions under different applied magnetic field (a) B = 0.113 T; (b) B = 0.114 T; (c) B = 0.115 T; (d) B = 0.116 T; (e) B = 0.117 T; (f) B = 0.118 T

图6 y和z方向都使用周期性边界条件时，kz = nz·2π/Lz，nz = 0、1、…、7且ky = 0的8个自旋波模在不同磁场下的演化(a) B = 0.113 T; (b) B = 0.114 T; (c) B = 0.115 T; (d) B = 0.116 T; (e) B = 0.117 T; (f) B = 0.118 T

Fig.7 Spin wave modes (a) k0 (kz = 0, ky = 0); (b) k1 (kz = 1·2π/Lz, ky = 0); (c) k4 (kz = 4·2π/Lz, ky = 0) resonate at B = 0.117 T, 0.1171 T, and 0.1153 T, respectively, when PBC is only along y direction. Spin wave modes (d) k0 and k1, (e) k4 resonate at B = 0.116 T and 0.1146 T, respectively, when no PBC is applied. (f) Evolution of spin wave modes with ky = n·2π/Ly, n = 0, 1, …, 7, kz = 0 at B = 0.116 T when no PBC is applied

图7 周期性边界条件只沿y方向时，自旋波模(a) k0 (kz = 0, ky = 0)在B = 0.117 T时共振; (b) k1 (kz = 1·2π/Lz, ky = 0) 在B = 0.1171 T时共振; (c) k4 (kz = 4·2π/Lz, ky = 0)在B = 0.1153 T时共振。当不使用周期性边界条件时，自旋波模(d) k0和k1在B = 0.116 T时共振; (e) k4在B = 0.1146 T时共振; (f)当不使用周期性边界条件时ky = n·2π/Ly，n = 0、1、…、7且kz = 0的8个自旋波模在B = 0.116 T时的演化

Fig.8 Spin wave intensity distribution in k space of three kinds of YIG conduit geometry (a) 2.56 μm long, 1.28 μm wide; (b) 2.56 μm long, 0.32 μm wide; (c) 10.24 μm long, 1.28 μm wide

图8 三种不同形状尺寸的YIG自旋波导的自旋波强度在k空间的分布(a) 长2.56 μm, 宽1.28 μm；(b) 长2.56 μm, 宽0.32 μm；(c) 长10.24 μm, 宽1.28 μm

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