Electron Spin Resonance Study on Local Structure of Manganese Ions Doped in Gamma-Aluminum Oxynitride Phosphors

We have studied the local structure of manganese ion doped in gamma aluminum oxynitride phosphors ( γ -AlON: Mn) using electron spin resonance (ESR) experiment. Six sharp peaks appear in ESR spectra of γ -AlON: Mn, together with five weak doublets. These structures are caused by the hyperfine interaction of 3 d electrons with the 55 Mn nucleus of spin I = 5/2. The six peaks are attributed to the allowed transitions (Δ M I = 0) between hyperfine splitting states of M s =(cid:156) 1/2. The five doublets are interpreted as the forbidden transitions (Δ M I =(cid:156) 1) between the hyperfine splitting states. The spectral feature of γ -AlON: Mn resembles with the ESR spectrum of Mn 2 + doped MgAl 2 O 4 spinel, in which Mn 2 + ions are substituted for tetrahedral Mg 2 + sites. Since γ -AlON is also of the spinel structure, it is suggested that Mn 2 + ions occupy tetrahedral Al 3 + sites. We further chased the effect of Mg 2 + co-doping on ESR spectra of Mn 2 + ions in γ -AlON, in order to elucidate the luminescence enhancement in γ -AlON: Mn, Mg. It turned out that the Mg 2 + co-doping increases Mn 2 + ions at tetrahedral Al 3 + sites.