A STUDY OF EXCHANGE INTERACTION IN CR3-DOPED CAY1-XGDXALO4()

The broadening of the R(1) lines of Cr3+ impurity ions in the substitu tionally disordered crystals CaY1-xGdxAlO4 (x = 0, 0.1, 0.5, 1) has be en studied. Fluorescence line narrowing removes the inhomogeneous broa dening created by variation in the crystal field and results in instru ment-limited spectral features for x = 0 and 0.1. Exchange interaction s between Cr3+ ions in octahedral positions and Gd3+ ions at second-ne arest-neighbour sites cause significant broadening of the narrowed R(1 ) line when x = 0.5 and 1. Comparisons of experimental and simulated s pectra have been used to estimate the magnitude of the exchange-coupli ng constant, J similar or equal to 2-3 cm(-1). Such simulations also s how that the selection rule for the (2)E --> (4)A(2) transition is bro ken by the Gd3+ spin in the Cr3+-Gd3+ exchange system.