Ultrafast Quenching of Ferromagnetism in InMnAs Induced by Intense Laser Irradiation

Abstract

Time-resolved magneto-optical Kerr spectroscopy of ferromagnetic InMnAs reveals two distinct demagnetization processes---fast ($<1\text{ }\text{ }\mathrm{ps}$) and slow ($\ensuremath{\sim}100\text{ }\text{ }\mathrm{ps}$). Both components diminish with increasing temperature and are absent above the Curie temperature. The fast component rapidly grows with pump power and saturates at high fluences ($>10\text{ }\text{ }\mathrm{mJ}/{\mathrm{cm}}^{2}$); the saturation value indicates a complete quenching of ferromagnetism on a subpicosecond time scale. We attribute this fast dynamics to spin heating through $p\mathrm{\text{\ensuremath{-}}}d$ exchange interaction between photocarriers and Mn ions, while the $\ensuremath{\sim}100\text{ }\text{ }\mathrm{ps}$ component is interpreted as spin-lattice relaxation.