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Highlights: [•] Dramatic structure variations of L10-FePt and superconducting YBCO thin films have been obtained by “simply” varying the laser frequency for pulsed laser deposition of these films, while keeping the thickness of the films constant. [•] The origins of structure variation with laser frequency for both Volmer-Weber mode grown FePt and Straski–Krastanov mode grown YBCO films are discussed and compared. [•] Deposition frequency increase from 1 to 6Hz leads to up to 20-fold enhancement of the coercive field in FePt films of constant thickness obtained by modification of demagnetization mechanism in laser frequency-varied structures (observed with MFM). [•] Varying growth kinetics of YBCO films by laser frequency leads to strong modification of dependence of critical current density on applied magnetic field (J c (B a )) with unexpected J c (B a ) reversal behavior with measurement temperature; such reversal behavior was never reported before; the mechanism of J c (B a ) modification is discussed. [ABSTRACT FROM AUTHOR]

Pulsed laser deposition (PLD) is employed to fabricate FePt L10 thin films from elemental targets. Dramatic structure variations are obtained by varying the laser frequency while keeping the thickness of the films constant. A new theoretical model based on the mean field approach is proposed, which quantitatively describes the structural changes obtained experimentally. The experiment and the model exhibit the opposite growth development to the trend reported for the modulated flux in the literature. The new model considers different growth rates in the lateral and transverse directions due to different responses of the normal and tangential film surfaces being deposited to the incident flux and the migration kinetics of adatoms and clusters. The quantitative results obtained confirm that the migration kinetics and self-assembly can easily be controlled by the PLD frequency which is consistent with the experiments. Magnetic properties of the films are shown to be extremely sensitive to the structure variations allowing practical tunability. (Some figures may appear in colour only in the online journal) [ABSTRACT FROM AUTHOR]

The dependence of properties in YBa2Cu3O7 (YBCO) films grown by pulsed laser deposition at different distances from the target to a substrate has been systematically studied. The target to substrate distance DTS is shown to enable simple means for tunability of the critical current density and microstructure of the YBCO films. The variation of structural and electromagnetic properties in the films as a function of DTS has been explained in terms of laser plume propagation model and thin film formation mechanism. [ABSTRACT FROM AUTHOR]

The vortex pinning model based on the presence of the large number of edge dislocations in high quality YBa2Cu3O7 (YBCO) films and multilayers has been refined. By introducing the pinning potential of a chain of individual edge dislocations, we have been able not only to describe the critical current density dependence on the applied magnetic field over its entire range, but also to extract the microstructural parameters in the films, such as interdislocation spacing and average domain size, without employing sophisticated microstructural analysis. The model applicability and its results have been verified with the help of microstructural characterization combined with magneto-optical imaging in YBCO films and multilayers with different properties. [ABSTRACT FROM AUTHOR]

Much denser YBa2Cu3O7 (YBCO) superconducting films at least 1 μm thick with smooth surfaces have been obtained after introducing (Y/Nd)BCO multilayered structures. A significant enhancement of current carrying abilities has been achieved in these pulsed laser deposited films. The critical current density (Jc) has been increased by a factor of up to three in the entire field range. The imitation of the (Y/Nd)BCO multilayered structure by using YBCO ‘interlayers’ has also exhibited a considerable improvement in the current carrying ability. Similarities and differences between these two ‘multilayering’ approaches, leading to the observed effects, are discussed. The presence of interfaces even without element variation is likely to be the key to the improvements observed. In order to further promote Jc enhancement, small ‘multilayered’ additions of silver (Ag) to the films and multilayers provide various results: (i) rather strong enhancement for rather thin films and low addition levels, (ii) considerable degradation for large addition levels, and (iii) much less pronounced effect for thicker films. The enhancement of Jc is observed in zero and low magnetic fields, but has almost no effect at higher fields. All these experimental observations are discussed in terms of pinning, transparency and structural modifications introduced during the deposition of the film structures. [ABSTRACT FROM AUTHOR]

Significant differences in superconducting and microstructural properties between two types of MgB2 films prepared by pulsed laser deposition were determined. A very high Hc2 — T slope of 1.1 T/K was achieved in the in situ film. The Jc — H curves of the in situ film also show a much weaker field dependence than that of the ex situ film. The magneto-optical (MO) images show that at 4 K the flux penetrates the in situ MgB2 film through random paths, while for the ex situ film, the flux penetration pattern is mostly repeatable, indicating a defect-controlled flux penetration. Microstructural study (transmission electron microscopy and atomic force microscopy) revealed a relatively big grain size in the ex situ film. The correlation between the super- conducting properties, microstructure and preparation conditions is discussed with regard to the two types of films. [ABSTRACT FROM AUTHOR]