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- Title
Phase transitions in the atomic, electronic, and magnetic subsystems of LaSrMnO films versus the synthesis temperature.
- Authors
Samoilenko, Z.A.; Okunev, V.D.; Pushenko, E.I.; Pafomov, N.N.; Szymczak, R.; Baran, M.; Lewandowski, S.J.
- Abstract
The evolution of the cluster structure in amorphous LaSrMnO films as synthesis temperature T s increases from 20 to 300°C is considered. Two order-disorder phase transitions with different scale parameters are observed. One of them, the aggregation of disordered atoms into small (∼20 Å) amorphous clusters at T s = 100°C, shows up as a sharp increase in the intensity of diffuse X-ray scattering (diffuse halo 1) with a simultaneous suppression of incoherent (background) scattering. At T s > 150°C, disordering dominates ( I incoh = I max) until the next stage of ordering sets in at T s = 250−300°C. At this stage, the crystalline phase forms from large (>100 Å) crystalline clusters. This amorphous-crystalline phase transition is characterized by the appearance of Debye lines and a reduction of the halo intensity. The structural phase transition to long-range order is accompanied by a decrease in the LaSrMnO resistivity from 1010 to 10 Ω cm and a change from the tunneling mechanism of conductivity involving metallic clusters (which is typical of granulated systems) to the hopping mechanism with a hop variable length following the Mott law ρ ∼ exp( T −1/4). In the magnetic subsystem, the paramagnetic-ferromagnetic phase transition occurs.
- Subjects
MAGNETIC films; LANTHANUM compounds; PHASE transitions; AMORPHOUS substances; ATOMS; X-ray scattering
- Publication
Technical Physics, 2006, Vol 51, Issue 6, p791
- ISSN
1063-7842
- Publication type
Article
- DOI
10.1134/S1063784206060168