Quantitative model for tunable microstructure in magnetic FePt thin films by pulsed laser deposition

Abstract

Golovchanskiy, I. A., Fedoseev, S. A. & Pan, A. V. (2013). Quantitative model for tunable microstructure in magnetic FePt thin films by pulsed laser deposition. Journal of Physics D: Applied Physics, 46 (21), 215502-1-215502-8.Quantitative model for tunable microstructure in magnetic FePt thin films by pulsed laser deposition AbstractPulsed 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. © 2013 IOP Publishing Ltd. Abstract. Pulsed laser deposition (PLD) has been employed to fabricate FePt L1 0 thin films from elemental targets. Dramatic structure variations have been 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 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.

Significant tunability of thin film functionalities enabled by manipulating magnetic and structural nano-domains

“…1 is well consistent with the key result obtained in Ref. 11 that the laser frequency affects the ratio of the out-of-plane to the in-plane growth. The decrease of in-plane to out-of-plane growth rates ratio at high surface coverage with increasing frequency leads to delayed impingement and coalescence of the islands and, as a consequence, to a structure with smaller islands.…”

“…The justification for the substrate material choice can be found elsewhere (see Ref. 11 and references therein). The base pressure in the PLD chamber was typically held at ≤ 10 −8 Torr that was reached after additional PLD chamber cleaning and baking routine.…”

“…The deposition temperature was chosen to ensure that the L1 0 structure of the FePt alloy forming at 500 • C 47-50 was complete 2,37,50-53 . The deposition process, facilitating almost equiatomic composition in the FePt epitaxial superstructures 54,55 , has been described elsewhere 11 . The deposition frequency was varied from 1 Hz to 6 Hz, so that the resultant thickness of the films was always approximately 20 nm.…”

“…In Ref. 11 , it was demonstrated that SFD of FePt films with identical H c reveal strong dipolar interactions between islands around the coercive field. However, the amplitude of the interaction appears to be proportional to the average island size.…”

“…For physical vapour deposition (PVD) technologies, this control is conventionally achieved by manipulating interdependent parameters, such as temperature, atmosphere, flux of material, resultant film thickness [1][2][3][4][5][6] and laser frequency [6][7][8][9][10] . In particular, the laser frequency for pulsed-based deposition (PLD) influences the film structure in many different ways, whose mechanisms can be contentious and not easily understood [7][8][9][10][11] . Thus, this interdependency is not trivial, impeding reproducibility and requiring sophisticated control with the help of, for example, reflection high-energy electron diffraction (RHEED) technique.…”