Electron spin resonance study of isolated Cr3+ ions and Cr3+ ion pairs in SrLaGaO4 and SrLaAlO4 single crystals

Abstract

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 observed for g = 1.980(2) in both materials. The zero-field splitting was small, therefore all allowed Cr3+ transitions nearly overlapped one another. For the nearest-neighbour Cr3+ ion pairs the ESR spectrum could only be observed for the S = 2 state, because broadening mechanisms did not affect this level. The coefficients of the isotropic exchange interaction J were determined from temperature dependencies of line intensity. The angular dependencies of ESR lines allowed the determination of the anisotropic exchange interaction constants. The following values have been found: J = 5.4(2)cm−1, g = 1.980(2), |DE| = 137(2) × 10−4cm−1, |EE| = 22(2) × 10−4cm−1 and J = 5.4(2) cm−1, g = 1.980(2), |DE| = 196(2) × 10−4cm−1, |EE | = 32(1) × 10−4cm−1 for SrLaGaO4 and SrLaAlO4 crystals, respectively.