Iron oxidation state in La0.7Sr1.3Fe0.7Ti0.3O4 and La0.5Sr1.5Fe0.5Ti0.5O4 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 M¨ossbauer 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 M¨ossbauer 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.