Observation of high coercivity in multiferroic lanthanum doped BiFeO < inf > 3 < /inf >

Abstract

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. © 2012 Elsevier B.V. All rights reserved.