ELECTRON-SPIN-RESONANCE STUDY OF ISOLATED CR3-PAIRS IN SRLAGAO4 AND SRLAALO4 SINGLE-CRYSTALS( IONS AND CR3+ ION)

The ESR spectrum of isolated Cr3+ ions and nearest-neighbour Cr3+ ion pairs in SrLaGaO4 and SrLaAlO4 single crystals have been studied at X- band. A nearly isotropic, single line of isolated Cr3+ ions was observ ed for g = 1.980(2) in both materials. The zero-field splitting was sm all, therefore all allowed Cr3+ transitions nearly overlapped one anot her. For the nearest-neighbour Cr3+ ion pairs the ESR spectrum could o nly be observed for the S = 2 state, because broadening mechanisms did not affect this level. The coefficients of the isotropic exchange int eraction J were determined from temperature dependencies of line inten sity. The angular dependencies of ESR lines allowed the determination of the anisotropic exchange interaction constants. The following value s have been found: J = 5.4(2) cm(-1), g = 1.980(2), \D-E\ = 137(2) x 1 0(-4) cm(-1), \E(E)\ = 22(2) x 10(-4) cm(-1) and J = 5.4(2) cm(-1), g = 1.980(2), \D-E\ = 196(2) x 10(-4) cm(-1) \E(E)\ = 32(1) x 10(-4) cm( -1) for SrLaGaO4 and SrLaAlO4 crystals, respectively.