We report the first successful preparation of thin films of Y-Ba-Cu-O superconductors using pulsed excimer laser evaporation of a single bulk material target in vacuum. Rutherford backscattering spectrometry showed the composition of these films to be close to that of the bulk material. Growth rates were typically 0.1 nm per laser shot. After an annealing treatment in oxygen the films exhibited superconductivity with an onset at 95 K and zero resistance at 85 and 75 K on SrTiO3 and Al2O3 substrates, respectively. This new deposition method is relatively simple, very versatile, and does not require the use of ultrahigh vacuum techniques.
SmCo based films containing 20 at. % Fe and with Sm varying from 15.5 to 17 at. % have been synthesized to show the transition from ordered CaCu5 to disordered TbCu7 phase. For either phase, the demagnetization energy present during deposition can result in films with the crystallite c axes randomly splayed onto the film plane. It has been possible to synthesize the high anisotropy CaCu5 phase with either a (200) or (110) texture by adjusting the sputtering parameters to correspond to either a relatively high or relatively low surface mobility during the film deposition. It has been possible to synthesize ordered CaCu5 type films with very low values of BR(⊥)/BR(∥)=0.042. Previously, SmCo based single phase TbCu7 structure films have been synthesized with close to the usual high energy product 2–17 compositions of nominally 7 at. % Cu and 2 at. % Zr. The films have been characterized by vibrating-sample magnetometer and superconducting quantum interference device magnetometry, x-ray diffraction, and scanning electron microscope measurements for composition and film morphology. The films have been directly crystallized onto heated substrates so that the crystallite c axes are predominantly randomly aligned in the film plane. The crystal structures observed could be switched from the ordered CaCu5 to the disordered TbCu7 phase for small variations in the Sm concentrations.
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Films of Sm–Co have been sputtered on heated polycrystalline Al2O3 substrates. The effect of variations of the Sm content on microstructure and hard magnetic properties was studied for otherwise constant process parameters. As generally observed, the samples possess a magnetic texture where the easy magnetization directions of the grains lay preferably in the film plane. For a lower Sm content the TbCu7-type structure is stabilized and for a higher Sm content the CaCu5-type structure is stabilized. The crossover occurs for a Sm content of around 17 at. %. Consistent with the changes in the intrinsic properties, coercivity increases and remanence decreases with increasing the Sm content. The grain size increases with increasing the Sm content and is attributed to a higher surface mobility during crystallization and grain growth. This behavior is also assumed to cause the improvement in the in-plane texture with increasing the Sm content, that had been quantified by magnetic and crystallographic investigations.
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