Iron oxidation state in La<inf>0.7</inf>Sr<inf>1.3</inf>Fe<inf>0.7</inf>Ti<inf>0.3</inf>O<inf>4</inf> and La<inf>0.5</inf>Sr<inf>1.5</inf>Fe<inf>0.5</inf>Ti<inf>0.5</inf>O<inf>4</inf> layered perovskites: Magnetic properties

Abstract

La0.5Sr1.5Fe0.5Ti0.5O4 and La0.7Sr1.3Fe0.7Ti0.3O4 solid solutions with the layered perovskite structure were synthesized using a solid state method. Structural properties of obtained samples were characterized using X-ray diffraction and X-ray fluorescence analyses. Magnetic properties were investigated using magnetometry, electron spin resonance (ESR) and Mössbauer spectroscopy methods. Based on magnetization and ESR measurements it was suggested the presence of Fe4+ ions in addition to trivalent iron ions that was exactly confirmed by Mössbauer spectroscopy investigations. Based on all experimental results one can suggest the presence of the electronic phase separation in the investigated samples – the simultaneous existence of the paramagnetic phase and magnetically correlated regions, which form due to the mixed-valence iron ions. So the paramagnetic phase with strong antiferromagnetic correlation exists in both samples, while the second phase is ferromagnetically and ferrimagnetically correlated regions in La0.5Sr1.5Fe0.5Ti0.5O4 and La0.7Sr1.3Fe0.7Ti0.3O4, respectively.