Intriguing structural and magnetic properties correlation study on Fe3+-substituted calcium-copper-titanate.

This communication presents a detailed study on a Fe3+ modified CaCu3Ti4O12 cubic perovskite system (CaCu3-xTi4-xFe2xO12 with x = 0.0-0.7) by performing X-ray powder diffractometry, DC SQUID magnetization and 57Fe Mössbauer spectroscopy. The first ever Mössbauer studies on the system supported the reported peculiarity of the structure. Mössbauer analysis for the compositions x = 0.1, 0.3, and 0.5 suggest Fe3+ ions in two different environments. The site with larger quadrupole splitting corresponds to Fe3+ in the octahedral symmetry, while the site with lower chemical shift and quadrupole splitting belongs to Fe3+ in the square-planar (A'-) configuration. With the increase in Fe-substitution, Fe3+ appears to prefer A'- symmetry. Antiferromagnetic features are retained up to x = 0.3, but weak ferromagnetic characteristics appear with higher Fe3+ substitution. The switching of antiferromagnetic to ferromagnetic behavior was related to the preferential occupation of Fe3+ in square-planar symmetry accommodating Cu2+.