Y0.225Sr0.775CoO3±δ thin films have been deposited on SrTiO3 (111), SrTiO3 (100), LaAlO3 (100) and MgO (111) single crystals substrates at 500°C by pulsed laser deposition (PLD) method. The optical measurements of these films were studied by ellipsometric method in the spectral range from 310 to 1240nm. The dependence of the optical constants, the refractive index (n), the extinction coefficient (k), the dielectric loss (ε‵) and the dielectric tangent loss (ε‵‵) of these films on the different single crystal substrates was also studied. The normal dispersion of refractive index of the films could be described using the Wemple–DiDomenico single oscillator method. The optical dispersion parameters Eo and Ed were determined according to the above oscillator method. Y0.225Sr0.775CoO3±δ thin films on different substrates have two direct and indirect allowed transitions corresponding to the energy gap Egd and Egind. The variation in either Egd or Egind with different substrates revealed that, orientation of the substrates affected the energy gap value. Other optical parameters such as the surface energy loss function and the volume energy loss function. were calculated optically. The effective mass of the film has also been calculated from both electrical and optical measurements

Ferromagnetic metal alloys are today commonly used in spintronic and magnetic data storage devices. These multicompound structures consist of several magnetic sublattices exhibiting both intrinsic and induced magnetic moments. Here, we study the response of the element-specific magnetization dynamics for thin film systems based on purely intrinsic (CoFeB) and partially induced (FePt) magnetic moments using extreme ultraviolet pulses from high-harmonic generation (HHG) as an element-sensitive probe. In FePt, on the one hand, we observe an identical normalized transient magnetization for Fe and Pt throughout both the ultrafast demagnetization and the subsequent remagnetization. On the other hand, Co and Fe show a clear difference in the asymptotic limit of the remagnetization process in CoFeB, which is supported by calculations for the temperature-dependent behavior of the equilibrium magnetization using a dynamic spin model. Thus, in this work, we provide a vital step toward a comprehensive understanding of ultrafast light-induced magnetization dynamics in ferromagnetic alloys with sublattices of intrinsic and induced magnetic moments.