Strong Impact of Cr Doping on Structural and Magnetic Properties of Bi_0.5La_0.5Fe_1−xCr_xO_3−δ

The structural and magnetic properties of Bi_0.5La_0.5Fe_1−xCr_xO_3−δ (x = 0, 0.05, 0.10, 0.20, and 0.40) compounds synthesized by a solid-state reaction method have been investigated. Rietveld refinement of x-ray and neutron powder diffraction data revealed a nonpolar orthorhombically distorted perovskite Pnma structure with long-range G-type antiferromagnetic (AFM) order in the studied samples. It was observed that substitution by Cr strongly influenced the morphology, crystalline, and magnetic properties of the samples. Interestingly, Cr doping led to an abrupt increase in the crystallite size from 31 nm for x = 0 to 740 nm for x = 0.40. This size change was accompanied by a decrease of microstrain by about twofold and a sudden change of the structural parameters. Magnetization measurements indicated the coexistence of ferromagnetic (FM) clusters with long-range AFM order. It was established that Cr doping leads to a suppression of the magnetic states. More interestingly, all of the samples demonstrated a spontaneous large exchange bias (EB) effect at room temperature, which is of great interest from the viewpoint of practical applications. The EB effect originates from pinning of uncompensated spins at the interfaces between FM clusters and the AFM matrix.