[11a-N401-6~8] 7.4 Buried interface sciences with quantum beam

△ [11a-N401-7] Ultrafast demagnetization in NiCo₂O₄ thin films probed by time-resolved microscopy

〇Ryunosuke Takahashi¹, Yoshiki Tani¹, Hirotaka Abe¹, Minato Yamasaki¹, Ikumi Suzuki², Daisuke Kan², Yuichi Shimakawa², Hiroki Wadati¹ (1.Univ. of Hyogo, 2.Kyoto Univ.)

Keywords:Ultrafast, Time resolved, Perpendicular magnetic anisotropy

Using a time-resolved magneto-optical Kerr effect (TR-MOKE) microscope, we observed ultrafast demagnetization of inverse-spinel-type NiCo2O4 (NCO) epitaxial thin films of the inverse spinel type ferrimagnet NCO 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 MOKE microscopy at 515 nm (the second harmonic). We successfully 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. These results, combined with the results of our x-ray photoemission spectroscopy study, indicate that this NCO thin film is a ferrimagnetic metal whose electronic structure deviates from the theoretically predicted half-metallic one.