Engineering of magnetic materials for developing better spintronic applications relies on the control of two key parameters: the spin polarization and the Gilbert damping, responsible for the spin angular momentum dissipation. Both of them are expected to affect the ultrafast magnetization dynamics occurring on the femtosecond timescale. Here, engineered Co₂MnAl_x Si_1‐x Heusler compounds are used to adjust the degree of spin polarization at the Fermi energy, P , from 60% to 100% and to investigate how they correlate with the damping. It is experimentally demonstrated that the damping decreases when increasing the spin polarization from 1.1 × 10⁻³ for Co₂MnAl with 63% spin polarization to an ultralow value of 4.6 × 10⁻⁴ for the half‐metallic ferromagnet Co₂MnSi. This allows the investigation of the relation between these two parameters and the ultrafast demagnetization time characterizing the loss of magnetization occurring after femtosecond laser pulse excitation. The demagnetization time is observed to be inversely proportional to 1 – P and, as a consequence, to the magnetic damping, which can be attributed to the similarity of the spin angular momentum dissipation processes responsible for these two effects. Altogether, the high‐quality Heusler compounds allow control over the band structure and therefore the channel for spin angular momentum dissipation.

中文翻译：

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工程Co2 MnAlx Si1-x Heusler化合物作为模型系统来关联自旋极化，固有吉尔伯特阻尼和超快退磁。

用于开发更好的自旋电子学应用的磁性材料工程依赖于两个关键参数的控制：自旋极化和吉尔伯特阻尼，吉尔伯特阻尼负责自旋角动量耗散。预计它们都会影响飞秒时标上发生的超快磁化动力学。在这里，设计的Co ₂ MnAl _x Si _{1 x} Heusler化合物用于将费米能量P处的自旋极化度从60％调整到100％，并研究它们与阻尼的关系。实验证明，当Co ₂的自旋极化从1.1×10 ^-3增加时，阻尼减小对于半金属铁磁体Co ₂ MnSi，具有63％自旋极化的MnAl达到4.6×10 ^-4的超低值。这样就可以研究这两个参数之间的关系，以及表征飞秒激光脉冲激发后发生磁化强度损失的超快退磁时间。观察到退磁时间与1- P成反比，因此与磁阻尼成反比，这可以归因于造成这两种效应的自旋角动量耗散过程的相似性。总之，高质量的Heusler化合物可以控制能带结构，因此可以控制自旋角动量耗散通道。