Transient Absorption Spectroscopy on MnPtGa using X-FAST Instrument

X-FAST installed at the University of Wisconsin-Madison is a pump-probe type setup with a conventional Ti:Sapphire femtosecond laser that delivers ultrashort pulses. One part of the laser beam goes towards producing XUV probe pulses by high-harmonic generation (HHG),while the other, serves as pump,at wavelength of 800 nm or 400 nm using nonlinear crystals. It covers the range from 40 eV to 72 eV, which encompasses core level photon absorption edges for many transition metals. All the experiments was done in transmission geometry and in room temperature. In this study, X-FAST was used to investigate MnPtGa thin films, a complex, very interesting and never studied metallic alloy of 15nm grown on a 50nm thin SiN membrane via epitixial growth technique. We first observed ground state XUV absorption spectra for the MnPtGa thin films. These provide element-selective "fingerprints" of the electronic structure and show core-level transitions associated with Mn and Pt atoms. Then we performed the time-resolved pump–probe measurements, using both 800 nm and 400 nm to photoexcite the sample and XUV probe pulses at various time delays to monitor its response. This experiment documented dramatic, ultrafast changes in the XUV absorption spectrum over time scales between tens and hundreds of femtoseconds on MnPtGa.