Stoichiometry, Phase, and Texture Evolution in PLD-Grown Hexagonal Barium Ferrite Films as a Function of Laser Process Parameters

TL;DR

This study investigates how laser process parameters in pulsed laser deposition affect the composition, structure, and magnetic properties of hexagonal barium ferrite films, identifying optimal conditions for high-quality film growth.

Contribution

It provides a systematic analysis of laser fluence effects on BaFe12O19 film stoichiometry, phase purity, and magnetic properties, highlighting the importance of process optimization.

Findings

Optimal laser fluence of 4.8 J/cm2 yields high-quality films

Higher fluences cause resputtering and degradation

Lower fluences lead to secondary phases and surface islands

Abstract

Barium hexaferrite (BaFe12O19 or BaM) films were grown on c-plane sapphire (0001) substrates by pulsed laser deposition (PLD) to evaluate the effects of the laser fluence on their composition, structure, and magnetic properties. Continuum's Surelite pulsed 266nm Nd:YAG laser was employed, and the laser fluence varied systemically between 1 and 5.7 [J/cm2]. Deviations from the stoichiometric transfer between the BaM targets and deposited thin films occurred as the laser fluence changed. The Fe to Ba ratio in the films increased with the laser fluence. The films deposited at the laser fluences below 4 J/cm2 showed undesirable 3-dimensional islands on the surface. Moreover, insufficient laser energy resulted in the deposition of some secondary phases, for example, barium monoferrite (BaFe2O4) and Magnetite (Fe3O4). On the other hand, laser fluences above 5 J/cm2 promoted resputtering and degraded the film quality, structure, and magnetic properties. BaM films deposited at 4.8 J/cm2 - the optimal laser fluence - showed excellent c-axis orientation perpendicular to the film plane with the anisotropy field of 16 kOe and saturation magnetization of 4.39 kOe. These results clearly demonstrate a strong influence of the laser parameters on the PLD-grown hexaferrite films and pave the path for the high-yield production using PLD systems.