近零有效磁化强度使自旋霍尔微振荡器实现超低阈值电流
Near-zero effective magnetization enabling ultra-low threshold currents in spin Hall micro-oscillators
浏览论文内容
中文总结 AI 辅助
该研究通过调控近零有效磁化强度，大幅降低自旋霍尔振荡器的阈值电流密度，实现了微米级自旋霍尔微振荡器，为超低功耗自旋霍尔器件提供了新策略。
中文摘要 AI 辅助
激发磁化动力学所需电流的降低是核心挑战，例如面向高能效磁子器件或基于振荡器的计算。自旋霍尔振荡器通常依赖大电流密度来补偿本征磁阻尼，因此这类系统通常在纳米尺度（自旋霍尔纳米振荡器，SHNOs）上研究，以适配适度电流和良好的散热几何结构。本文证明，调控近零有效磁化强度（$M_\text{eff}$）可大幅降低自旋霍尔振荡器的磁化振荡阈值电流密度，这使得激发横向尺寸达微米级的相对大尺寸系统成为可能，即所谓的“自旋霍尔微振荡器”（SHMOs）。利用微聚焦布里渊光散射光谱，我们对基于W/CoFeB/MgO/Ta、具有近零$M_\text{eff}$的SHMOs的阈值电流密度进行量化，观测到阈值电流密度低至$J_\text{th}$ = (0.292 $\textpm$ 0.025) $\times 10^{10}$ A/m$^{2}$，与最新报道的SHNOs相比降低了两个数量级以上。通过系统的微磁模拟，我们研究了宏观自旋近似的失效，并强调了$M_\text{eff}$对自旋电流作用下磁化动力学的重要影响。本研究确立了$M_\text{eff}$调控作为实现超低功耗自旋霍尔振荡器和高能效磁化调控的有效策略。
英文摘要
Reducing the electrical current required to excite magnetization dynamics is a central challenge, e.g. for energy-efficient magnonic devices or oscillator-based computing. Spin Hall oscillators typically rely on large current densities to compensate intrinsic magnetic damping, so these systems are usually studied on the nanoscale (Spin Hall Nano Oscillators, SHNOs) to work with moderate currents and a favorable heat dissipation geometry. Here, we demonstrate that engineering a near-zero effective magnetization ($M_\mathrm{eff}$) enables a drastic reduction of the magnetization oscillation threshold current density for Spin Hall oscillators. This makes it possible to excite even comparably large systems with micrometer lateral sizes, so-called "Spin Hall Micro-Oscillators" (SHMOs). Using micro-focused Brillouin light scattering spectroscopy, we quantify the threshold current density in SHMOs based on W/CoFeB/MgO/Ta with near-zero $M_\mathrm{eff}$. We observe threshold current densities as low as $J_{\mathrm{th}}$ = (0.292 $\pm$ 0.025) $\times 10^{10}$ A/m$^{2}$, representing a reduction of more than two orders of magnitude compared with most recent reported SHNOs. Using systematic micromagnetic simulations, we investigate the breaking down of the macrospin approximation and underline the high influence of $M_\mathrm{eff}$ on magnetization dynamics under applied spin currents. Our results establish $M_\mathrm{eff}$ engineering as a powerful strategy for realizing ultra-low-power spin Hall oscillators and energy-efficient magnetization control.
