Synergistic effect of trivalent (Gd3+, Sm3+) and high-valent (Ti4+) co-doping on antiferromagnetic YFeO3
Monophasic polycrystalline powders of Y1−xRxFe1−(4/3)yTiyO3 (R = Sm, Gd; x = 0.05, 0.10, 0.15; y = 0.05) were successfully synthesized via a low temperature solid-state synthesis route. The X-ray diffraction and Raman spectroscopy studies indicate that all the calcined powders with R3+ (Gd3+, Sm3+) at Y3+ and Ti4+ at Fe3+ sites were crystallized in an orthorhombic phase associated with a change in lattice parameters. The Williamson–Hall method employed to calculate the strain revealed that the strain increased with the increased concentration of dopants ((Gd3+, Sm3+) at Y3+) compared to an increase in the size of crystallites, corroborating the findings of SEM. Analysis of diffuse reflectance spectra indicated a drop in bandgap from 1.93 eV to 1.86 eV and 1.96 eV to 1.91 eV for Gd, Ti co-doping and Sm, Ti co-doping respectively, demonstrating the capacity of the synthesized powders to absorb visible light. Absorbance spectra also revealed the existence of mixed states of Fe3+ and Fe4+ which was corroborated by XPS studies. The magnetic hysteresis loop analysis at room temperature illustrated that with co-doping, there is a strong enhancement in magnetization as well as coercivity, suggesting a strong transition from anti-ferromagnetic behaviour to ferromagnetic behaviour. Pertaining to the greatly improved optical and magnetic properties with the addition of (Gd3+, Sm3+) at Y3+ and Ti4+ at Fe3+ sites, these materials are anticipated to be of potential use in various applications.