Change of optical band gap and magnetization with Mn concentration in Mn-doped AlN films

Mn-doped AlN films were prepared by magnetron reactive sputtering system. The preparation conditions were optimized to give pure single-phase AlMnN films. The films were deposited on quartz substrates. The single-phase films were obtained in argon-nitrogen pressure of 6 mTorr and a substrate temperature of 300 deg. C. The films typically had a thickness of 0.4 μm. The XRD pattern indicated a pure AlMnN phase. The concentration of Mn was determined by energy dispersive X-ray and X-ray photoemission spectrometry. The saturation magnetization (M s) decreased with increasing Mn concentration exponentially. A maximum M s of 9.58 emu/cm3 was obtained at room temperature with Mn doping of 4.5%. The optical band gap decreased from 6.2 to 4.95 eV with increasing Mn concentration from 0 to 13.6% with same trend to magnetic properties. The change of the optical band gap was strongly correlated with magnetization data