Ohkoshi Shin-Ichi, Imoto Kenta, Namai Asuka, Yoshikiyo Marie, Miyashita Seiji, Qiu Hongsong, Kimoto Shodai, Kato Kosaku, Nakajima Makoto
Department of Chemistry, School of Science , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku , Tokyo 113-0033 , Japan.
Department of Physics, School of Science , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku , Tokyo 113-0033 , Japan.
J Am Chem Soc. 2019 Jan 30;141(4):1775-1780. doi: 10.1021/jacs.8b12910. Epub 2019 Jan 15.
Light- or electromagnetic wave-responsive magnetism is an attractive issue in spin chemistry and optical materials science. Herein we show the magnetization reversal induced by visible-light pulsed laser and the ultrafast dynamic magnetooptical effect caused by terahertz (THz) pulsed laser irradiation onto chemically synthesized magnetic films based on gallium-titanium-cobalt-substituted ε-FeO (GTC-ε-FeO) and ε-FeO nanoparticles. Visible-light pulsed laser irradiation switches the sign of the Faraday effect in GTC-ε-FeO films. On the other hand, irradiating the ε-FeO film with pulsed THz light induces an ultrafast Faraday rotation in an extremely short time of 400 fs. The time evolution dynamics of these ultrafast magnetooptical effects are theoretically demonstrated by stochastic Landau-Lifshitz-Gilbert calculations of a nanoparticle model that considers all motions of the individual spins. These ε-iron oxide magnetic nanomaterials are expected to contribute to high-density magnetic memory media or high-speed operation circuit magnetic devices.
光或电磁波响应磁性是自旋化学和光学材料科学中一个引人关注的问题。在此，我们展示了基于镓 - 钛 - 钴取代的ε - 氧化铁（GTC - ε - FeO）和ε - FeO纳米颗粒的化学合成磁性薄膜上，可见光脉冲激光诱导的磁化反转以及太赫兹（THz）脉冲激光辐照引起的超快动态磁光效应。可见光脉冲激光辐照会改变GTC - ε - FeO薄膜中法拉第效应的符号。另一方面，用脉冲太赫兹光辐照ε - FeO薄膜会在极短的400飞秒时间内诱导超快法拉第旋转。通过考虑单个自旋所有运动的纳米颗粒模型的随机朗道 - 里夫希茨 - 吉尔伯特计算，从理论上证明了这些超快磁光效应的时间演化动力学。这些ε - 氧化铁磁性纳米材料有望为高密度磁存储介质或高速运行电路磁性器件做出贡献。
