Tuning the decay of Mn2+ emission via magnetically coupling with Cr3+ in ZnGa2O4

Abstract

Mn2+ emission tends to saturate under irradiation of high flux light, which is first caused by its long decay lifetime ascribing to the spin-forbidden transition of 4T1 → 6A1. Coupling with hetero-transition metal ions to alter the spin state of Mn2+ is a potential way to improve it. In this research, we attempt to provide evidence for the exchange coupling interaction between Mn2+ and Cr3+ in the ZnGa2O4 material and figure out the lifetime variation of Mn2+ emission. A faster decay of Mn2+ emission is achieved when elevating the Cr3+ concentration rather than the Mn2+ concentration, and the dominant cause of energy transfer from Mn2+ to Cr3+ is ruled out. Electron spin resonance results illustrate the stronger spin relaxation of Mn2+ 3d electrons imposed by Cr3+ than that imposed by the other Mn2+ ions. These phenomena suggest the existence of coupling between Mn2+ and the neighboring Cr3+, which is evidenced by the first principles calculation. It is further convinced by the total spin quantum number for the Mn2+, Cr3+ singly doped, and codoped systems, which is close to 3/2, 3/2, and 5/2, respectively, according to the derived magnetic susceptibility data. This research proposes a strategy for anti-saturating the Mn2+ emission in phosphors.