Observation of high coercivity in multiferroic lanthanum doped BiFeO3

LaxBi1−xFeO3 (x = 0.0–0.4) ceramics are synthesized by solid state reaction method. An increase in La results systematic decrease in rhombohedral (∼92.4% to ∼ 58.39%) and increase in orthorhombic phase (∼7.59% to ∼41.60%). The structural transition is further confirmed by the changes observed in Raman vibrational modes. A significant enhancement in the dielectric constant by two to three times is observed with La doping. Upon the La doping, the canted anti-ferromagnetic behavior of BiFeO3 turns to weak ferromagnetic. A huge enhancement in remanent magnetization (Mr) and coercivity (HC) of the order of 1.21 T is observed even for a small doping of x = 0.05. The improvement in the magnetic properties of La doped ceramics over BiFeO3 is due to the destruction of spin cycloid with the substitution of La. A cusp at 50 K in the M–T curve reveals a spin glass nature of these samples. Anti-ferromagnetic Néel temperature (TN) increases with x. From the high temperature M–T curve, it is revealed that these ceramics exhibit a large magnetic irreversibility confirming the spin glass state.

► Two phase model is used to refine the structure.
► The quantitative estimates of phases as a function of doping are presented.
► Effect of La doping on the dielectric, magnetic properties is reported.
► High coercivity ∼1.5 Tesla is observed for La doped BiFeO3 samples.
► TN increases with increase in La doping.