Comparative study of magnetic and optical properties of Bi0.95La0.05Fe0.8M0.2O3 (MÂ =Â Cr, Co, Al) ceramics

Bi0.95La0.05Fe0.8M0.2O3 (M = Cr, Co, Al) ceramics have been prepared by high pressure synthesis and their structure, magnetic, thermal, and optical properties have been investigated. X-ray diffraction suggests the pure phase formation with rhombohedral structure in all samples. The structural distortion induced by dopants is further analyzed by Raman spectra. The SEM investigation reveals that Cr and Al substitution does not affect the morphologies of Bi0.95La0.05FeO3 ceramics, while Co substitution significantly reduces the grain sizes and uniforms the morphology. The effect of substitution on the magnetic properties of Bi0.95La0.05FeO3 is different depending on M due to different mechanisms. More interestingly, Co substitution induces a change in the spin structure from a cycloidal space modulated spin structure to a collinear G-type antiferromagnetic structure, which results in obviously enhanced magnetization at room temperature. Optical studies show a sharp absorption in the visible region for all samples. The band gap values of Bi0.95La0.05FeO3 and Bi0.95La0.05Fe0.8M0.2O3 ceramics with M = Cr, Co, and Al are estimated to be 2.30, 2.06, 2.12 and 2.27 eV, respectively.