Influence of Jahn-Teller Cu (3d) ion on structural and magnetic properties of Al-Cr co-substituted CuFeO.

Four specimens of two compositions of the spinel oxide system CuAlCrFeO with x = 0.2 and 0.6 have been synthesized by double sintering ceramic technique with different thermal history i.e. quenched and slow-cooled. X-ray diffractometry has confirmed that tetragonal distortion is present in slow-cooled sample, while it is absent in quenched sample. The lower value of saturation moment compared to Neel's moment for each composition is explained by invoking random canting of spins model. Hyperfine interaction parameters: nuclear hyperfine field, quadrupole splitting (shifts), isomer shift and Fe ion distribution are deduced through computer simulation of Mössbauer spectra. Fe Mössbauer spectra recorded at room temperature show the effect of magnetic dilution of inter-sublattice ( A- B) interaction (frustration) more in case of quenched-sample compared to slow-cooled one. FTIR spectra also corroborate the influence of Jahn-Teller (J-T) distortion of octahedral void arising due to larger Cu ion occupancy at octahedral sites. The force constants are also estimated from FTIR spectra. [ABSTRACT FROM AUTHOR]