Effect of conventional thermal annealing（CTA） and rapid recurrent thermal annealing（RRTA） processes on crystal structure,mi-crostructure,and magnetic properties of the SmCo-based films were investigated.The results indicated that the CTA-treated films exhibited poor permanent magnetic properties,and a low intrinsic coercivity of 72.8 kA/m was observed.Wide hysteresis loop was obtained for the RRTA-treated films,providing better permanent magnetic properties.The intrinsic coercivity reached 312.0 kA/m.According to the X-ray diffraction（XRD） and atomic force microscopy（AFM） results,the magnetic properties of the CTA-treated films and RRTA-treated films were found to be correlated with the crystal structure and microstructure,which were strongly determined by the annealing treatment.CTA treatment led to poor crystallization effects for the films,and a rough surface（RMS=3.47 nm and P-V=35.42 nm） and large grain size of 92.7 nm were observed correspondingly.However,the RRTA treatment exhibited great contributions on the crystallization of the films,which is accountable for the smooth surface（RMS=2.047 nm and P-V=16.43 nm） and fine grain size of 60.8 nm.
It is believed that the ultrafast demagnetization process in ferromagnetic film is intrinsically a thermal effect,which is induced by ultrafast laser pulses.We present experimental evidence that such ultrafast demagnetization of the NiFe thin film can radiate electromagnetic waves in the terahertz range.We also demonstrate that the magnitude of the terahertz electromagnetic pulse emitted from ferromagnetic films alter pulsed laser excitation can be tuned by the Gilbert damping factor α,which is conventionally used to describe damping of GHz precession motion of magnetization.Different damping factors are obtained by varying the normal metal film adjacent to the magnetic film via spin pumping.The measured radiated electric field in the far field is found to be proportional to the Gilbert damping factor.
