Determination of exchange parameters of Cr3+ pairs in MgAl2O4 by optical measurements

Abstract

The emission and luminescence excitation spectra of nearest‐neighbor Cr³⁺ pairs in spinel MgAl₂O₄ have been studied. Analyses of these spectra yield the (⁴A₂, ⁴A₂) ground state level splittings. They are described by −JS̄₁⋅S̄₂+j (S̄₁⋅S̄₂)², with S₁=S₂=3/2, J=−(29±3) cm⁻¹, and j=−(3±2) cm⁻¹. A couple of transitions to the first excited pair state (⁴A₂, ²E) have been observed in the excitation spectrum; however, the data are insufficient to determine the parameters describing the exchange splittings of the excited state.