Iron substitution in PrAlO3 perovskite leading to structural transformation and multiferroicity

Abstract

Recognizing the crucial properties exhibited by FeAlO3 perovskite, its stabilization with the inclusion of bigger sized Pr3+ (f-block ion) in place of Fe3+ (d-block ion) is examined by preparing the samples employing an epoxide mediated sol-gel route and characterizing them extensively. Up to 40 mol % substitution of iron, hexagonal PrAlO3 with rhombohedral symmetry (R-3c spacegroup) was retained. At 50 mol % of iron substitution, it transformed into orthorhombic symmetry (Pnma spacegroup). At 80 mol % substitution of iron, X-ray pattern was amorphous. The metal-oxide bonding and symmetries were further verified by FTIR and Raman measurements. EPR and XPS measurements, performed at room temperature, confirmed the presence of Fe2+ and Fe3+ in the samples. Besides, praseodymium existed in III and IV oxidation states in these samples. Both field and temperature-dependent measurements showed ferromagnetic/ferrimagnetic behavior in the iron substituted samples. The ferrimagnetic transition occurred above room temperature (321 K) in 70 mol % iron substituted PrAlO3. Such a high TF is not reported till now among the available polymorphs of PrAlO3 or FeAlO3. 50 and 70 mol % iron substituted PrAlO3 samples showed ferroelectric behavior at room temperature, qualifying them to be multiferroics.