The development of energy efficient techniques for the generation of spin waves (magnons) is important for the implementation of low-dissipation spin-wave-based logic circuits and memory elements. A promising approach to achieve this goal is based on the injection of short strain pulses into ferromagnetic films with a strong magnetoelastic coupling between the spins and strains. Here, we report micromagnetoelastic simulations of the magnetization and strain dynamics excited in ${\mathrm{Fe}}_{81}{\mathrm{Ga}}_{19}$ films by picosecond and nanosecond acoustic pulses created in a GaAs substrate by a transducer subjected to an optical or electrical impulse. The simulations performed via the numerical solution of the coupled Landau-Lifshitz-Gilbert and elastodynamic equations show that the injected strain pulse induces an inhomogeneous magnetization precession in the ferromagnetic film. The precession lasts up to 1 ns and can be treated as a superposition of magnon modes having the form of standing spin waves. For ${\mathrm{Fe}}_{81}{\mathrm{Ga}}_{19}$ films with a nanoscale thickness, up to seven (six) distinct modes have been revealed under free-surface (pinning) magnetic boundary conditions. Remarkably, magnon modes with frequencies over 1 THz can be excited by acoustic pulses with an appropriate shape and duration in films subjected to a moderate external magnetic field. This finding shows that short strain pulses represent a promising tool for the generation of THz spin waves necessary for the implementation of high-speed magnonic devices.

中文翻译：

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短应变脉冲激励磁弹性薄膜中的高频磁振子模式

用于产生自旋波（磁振子）的节能技术的发展对于实现低耗散基于自旋波的逻辑电路和存储元件非常重要。实现此目标的一种有前途的方法是基于在自旋和应变之间具有强磁弹性耦合的短应变脉冲注入铁磁膜中。在这里，我们报告磁化和应变动力学激发的微磁弹性模拟${铁}_{81}{嘎}_{19}$通过受到光或电脉冲的换能器在GaAs基板中产生的皮秒和纳秒声脉冲产生薄膜。通过耦合的Landau-Lifshitz-Gilbert数值解和弹性动力学方程进行的仿真表明，注入的应变脉冲在铁磁膜中引起了不均匀的磁化旋进。进动持续时间长达1 ns，可以看作是具有自旋波形式的磁振子模式的叠加。对于${铁}_{81}{嘎}_{19}$在自由表面（钉扎）磁边界条件下，已揭示出具有纳米级厚度的薄膜，多达七（六）种不同的模式。值得注意的是，在受到中等外部磁场作用的薄膜中，具有适当形状和持续时间的声脉冲可以激发频率超过1 THz的磁振子模式。这一发现表明，短应变脉冲代表了一种有前途的工具，可用于生成高速磁电设备必需的太赫兹自旋波。