XRD and Mossbauer studies of crystallographic and magnetic transformations in synthesized Zn-substituted Cu-Ga-Fe compound

摘要

System of samples in the form of Cu1-xZnxFe2-yGayO4 with (0.0less than or equal toxless than or equal to1.0, y = 0.0 and 1.0) is synthesized. X-ray diffraction study confirms the presence of a single-phase structure, where tetragonal unit cell is obtained for samples CuFe2O4 and CuGaFeO4 with c/a > 1. At compositional parameter x greater than or equal to 0.25, tetragonal-to-cubic transformation occurs. The determined lattice parameter a for the cubic samples is found to decrease with increasing Zn content x. Fe-57 Mossbauer measurements at 293, 77 and 12 K show characteristic spectra of paramagnetic, magnetic, and electronic types for the different compositions. Cation distribution obtained from the spectral analysis at 12 K revealed transformation from the ferrimagnetic inverse spinel of CuFe2O4 to the antiferromagnetic normal spinel of ZnFe2O4. Hyperfine parameters are found to be strongly dependent on temperature and concentration parameter X. Low-temperature measurements are carried out using installed and well-calibrated closed-cycle variable temperature cryostat Model REF-399-D22. Low vibration is obtained through bellows, spacer, and exchange gas isolation and a difference of 0.018 mm s(-1) between the FWHM of a pure iron foil at room temperature and 12 K is achieved. (C) 2004 Elsevier Inc. All rights reserved.