Using a time-resolved magneto-optical Kerr effect microscope, we observed ultrafast demagnetization of inverse-spinel-type ferrimagnet NiCo₂O₄ (NCO) epitaxial thin films with perpendicular magnetic anisotropy. This microscope uses a pump-probe method, where the sample is pumped at 1030 nm, and magnetic domain images are acquired via magneto-optical Kerr effect microscopy at 515 nm (the second harmonic). We observed the dynamics of the magnetic domain of the NCO thin film via laser irradiation and obtained a demagnetization time constant of approximately 0.4 ps. This time constant was significantly smaller than the large time constants reported for other half-metallic oxides. This timescale of ∼0.4 ps agrees with the spin polarization of ∼0.7 determined by tunnel magnetoresistance [Shen et al., Appl. Phys. Lett. 117, 042408 (2020)].

中文翻译：

---

时间分辨显微镜探测 NiCo2O4 薄膜中的超快退磁

使用时间分辨磁光克尔效应显微镜，我们观察到反尖晶石型亚铁磁体 NiCo ₂ O _{4 的}超快退磁(NCO) 具有垂直磁各向异性的外延薄膜。该显微镜使用泵浦探针方法，其中样品在 1030 nm 处泵浦，磁畴图像通过磁光克尔效应显微镜在 515 nm（二次谐波）处获取。我们通过激光照射观察了 NCO 薄膜磁畴的动力学，并获得了大约 0.4 ps 的退磁时间常数。这个时间常数明显小于其他半金属氧化物报道的大时间常数。这个 ~0.4 ps 的时间尺度与隧道磁阻确定的 ~0.7 自旋极化一致 [Shen等人。，应用程序。物理。莱特。117 , 042408 (2020)]。