Investigating the impact of increasing the N2/(Ar+N2) gas flow ratio in the presence of residual oxygen on magnetic properties of reactively sputter-deposited thin films of amorphous Al–O–N alloy

In the present work, we have reported the impact of increasing N₂/(Ar + N₂) gas flow ratio in the presence of residual oxygen on the magnetic properties of reactively sputter-deposited thin films of amorphous Al–O–N alloy. Amorphous Al–O–N alloy thin films were deposited via reactive sputtering of an aluminum target in the presence of residual oxygen, using an Ar/N₂ gas mixture with increasing N₂/(Ar + N₂) gas flow ratios of 10 %, 20 %, and 50 %, respectively. Microstructural analysis confirms that all three films exhibit amorphous characteristics with short-range ordering. Chemical analysis indicates that a portion of aluminum reacts with nitrogen to form AlN, while the remaining film primarily consists of the Al(NO_y)_x phase, containing oxygen vacancy (O_V) sites. At 300 K, all three films display superparamagnetic (SPM) behavior, indicating the presence of nano-scale single-domain magnetic particles. However, an increase in the N₂/(Ar + N₂) gas flow ratio systematically enhances both the bulk saturation magnetization and the magnetic volume fraction in the films. This enhancement correlates well with the increased formation of the Al(NO_y)_x phase containing O_V sites. These findings suggest that oxygen vacancies within the Al(NO_y)_x phase play a key role in inducing magnetism in Al–O–N alloy thin films at 300K that can be tailored by manipulating the N₂/(Ar + N₂) flow ratios during sputter deposition. Therefore, the present study provides a new insight into tailoring the magnetic properties of amorphous Al-O-N alloy thin films by precisely controlling the deposition conditions, particularly the gas flow ratio in the presence of residual oxygen.