Fig. 1. (a) THz time domain transmission signals of LCMO film on a 0.5-mm LAO substrate at 100 K, 200 K, and 300 K, respectively, (b) THz transmission signals of 0.5-mm LAO substrate at 100 K, 200 K, and 300K, respectively. The green rectangles highlight the echo pulse occurring at the interface of LCMO/LAO (a) and vacuum/LAO (b)

Fig. 2. (a) THz electric field amplitude transmission of LCMO film as a function of temperature at several frequencies, (b) Temperature dependent magnetization of LCMO film, as measured in field cooling condition with the applied magnetic field of 500 Oe, (c) Conductivity (real part) of LCMO film with temperature at several frequencies, (d) dM/dT as a function of temperature for the LCMO film

Fig. 3. (a) The THz echo pulses in time domain at 198 K, 204 K, 210 K, (b) The diagram of terahertz pulses come across sample (La_0.7Ca_0.3MnO₃ /LaAlO₃) at different temperature

Fig. 4. The complex conductivity of LCMO film at four selected temperatures （a）40 K， （b）200 K， （c）220 K， and （d）290 K Note： The black and red dots are denoted for real and imaginary part of conductivity， respectively. In （a） and （b）， the solid lines are fitting curves with Drude model. In （c） and （d）， the solid lines are fitting curves with Drude-Lorentz model. The fitting parameters are presented in Fig. 5

Fig. 5. The temperature dependence of plasma frequency （ω_p） （a）， electrons scattering time （τ） （b）， and Lorentz resonance frequency （ω₀） （c） of the La_0.7Ca_0.3MnO₃ film in the temperature range from 40 K to 290 K