The BaFe12O19 thin films were grown on (0001)-oriented Al2O3 substrates (CRYSTAL GmbH) using a pulsed laser deposition (PLD) system with a base pressure of 2 × 10−7 torr (3). The PLD system used a 248-nm KrF excimer laser, and the energy fluence of the laser beam was 1.7 J/cm2. The target-to-substrate distance was set to 5 cm. The BaFe12O19 target was preablated, while the T ramped up to 800°C. During the deposition, the oxygen pressure was kept at 75 mtorr. The laser pulse rate ramped from 1 to 5 pulse/s with equal steps during the initial 5 min, and it was kept at 5 pulse/s for the rest, which corresponds to a film growth rate of about 2.5 Å/min. The film was annealed in situ at 800°C in 400-torr oxygen for 10 min and was then cooled to room temperature at a rate of 2°C/min.

The growth of the Bi2Se3 film was performed in a molecular beam epitaxy (MBE) system with a base pressure of 2 × 10−10 torr or lower. High-purity Se (99.999%) and Bi (99.999%) targets were supplied from solid sources in Knudsen cells to maintain a flux ratio of 16.8:1. Before the growth, the BaFe12O19 film was heated to 340°C first. The T was subsequently reduced to 225°C, and at this T, a Bi2Se3 buffer layer (<1 nm) was deposited for 90 s to facilitate growth. The film T was then increased to 290°C. Once at this T, Bi2Se3 deposition continued at 2.34 Å/min, while the T continually ramped to an ultimate T of 320°C. After cooling the film to room T, a thin Te capping layer (~2 nm) was deposited using Te (99.9999%) also from a Knudsen cell to prevent the oxidization of the Bi2Se3 film.

The Pt layer was deposited in a magnetron sputtering system with a base pressure of 2 × 10−8 torr. The deposition was at room temperature, and the deposition rate was about 0.33 Å/s.

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