Variety of LaSrMnO structures induced by growth conditions and laser irradiation |
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Authors: | Z. A. Samoilenko V. D. Okunev E. I. Pushenko T. A. D’yachenko A. Cherenkov P. Gierlowski S. J. Lewandowski A. Abal’oshev A. Klimov A. Szewczyk |
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Affiliation: | (1) Galkin Physicotechnical Institute, National Academy of Sciences of Ukraine, Donetsk, 83114, Ukraine;(2) Instytut Fizyki PAN, Al. Lotnikov 32/46, 02-668 Warszawa |
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Abstract: | Crystallographic phase transitions in perovskite-like LaSrMnO metallic oxides are studied. The transitions are induced when internal stresses generated during film synthesis (at temperatures between 450 and 730°C) vary (decrease or increase) upon subsequent irradiation by a KrF laser emitting in the UV range. As the synthesis temperature T s grows, the rhombohedral-to-orthorhombic phase transition occurs at 650–670°C. The resistivity is shown to be either temperature-independent, ρ(T)=const, at T<T crit, or varies and reaches a maximum, ρ(T)=ρmax, at the Curie temperature T c. Optical transmission spectra taken at photon energies ℏω=0.5–2.5 eV exhibit both a high (0.8–0.9) and low (0.1–0.3) transmission coefficient t, depending on the synthesis temperature. As follows from X-ray diffraction data, the laser irradiation causes a phase transition only in LaSrMnO films grown at T s<650°C. Phases of different size scales appear: the long-range-order orthorhombic matrix and mesoscopic-range-order rhombohedral clusters are observed in the films grown at T s=450–550°C and the rhombohedral matrix with orthorhombic clusters, in the films grown at T s=550–650°C. |
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