Abstract
We report a universal terahertz (THz) emission behavior from simple Ni, Fe, and Co metallic ferromagnetic films, triggered by the femtosecond laser pulse and subsequent photoinduced demagnetization on an ultrafast time scale. THz emission behavior in ferromagnetic films is found to be consistent with initial magnetization states controlled by external fields, where the hysteresis of the maximal THz emission signal is observed to be well-matched with the magnetic hysteresis curve. It is experimentally demonstrated that the ultrafast THz emission by the photoinduced demagnetization is controllable in a simple way by external fields as well as pump fluences.
Highlights
We report a universal terahertz (THz) emission behavior from simple Ni, Fe, and Co metallic ferromagnetic films, triggered by the femtosecond laser pulse and subsequent photoinduced demagnetization on an ultrafast time scale
We report our experimental investigation on the field-dependent THz emission by ultrafast photoinduced demagnetization in 30-nm Fe, Ni, and Co films with variation of external fields, where a universal THz emission behavior is regardless of film elements is clearly observed with field-tunability
The electric field profile of emitted THz wave upon ultrafast demagnetization of Fe, Ni, and Co films is illustrated in Fig. 1a for several magnetic states including oppositely saturated states
Summary
We report a universal terahertz (THz) emission behavior from simple Ni, Fe, and Co metallic ferromagnetic films, triggered by the femtosecond laser pulse and subsequent photoinduced demagnetization on an ultrafast time scale. We have reported our direct observation of THz emission and photoinduced demagnetization/remagnetization signals in Co films with comparison to each other, demonstrating that the THz emission from the ultrafast demagnetization becomes dominant in relatively thick (> 30 nm) Co films, regardless of selection of capping layers[18]. We report our experimental investigation on the field-dependent THz emission by ultrafast photoinduced demagnetization in 30-nm Fe, Ni, and Co films with variation of external fields, where a universal THz emission behavior is regardless of film elements is clearly observed with field-tunability
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