Abstract:
Undoped BiFeO3, Gd doped Bi0.9Gd0.1FeO3, and Gd-Ti co-doped Bi0.9Gd0.1Fe1−xTixO3
(x = 0.10, 0.20) materials were synthesized to report their temperature dependent
electric and magnetic properties. The structural analysis and phase identification of
these multiferroic ceramics were performed using Rietveld refinement. The Rietveld
analysis has confirmed the high phase purity of the 10% Gd-Ti co-doped
Bi0.9Gd0.1Fe0.9Ti0.1O3 sample compared to that of other compositions under
investigation. The major phase of this particular composition is of rhombohedral R3c
type structure (wt% > 97%) with negligible amount of impurity phases. In terms of
characterization, the magnetic properties of this co-doped ceramic system were
addressed by applying substantially higher magnetic fields than that applied in
previously reported investigations of this material system. Both the coercive fields
and remanent magnetizations were higher for 10% Gd-Ti co-doped
Bi0.9Gd0.1Fe0.9Ti0.1O3sample than those for other materials. The dependence of
temperature on their magnetization behaviour have been investigated elaborately.
Unexpectedly, the coercive fields of this multiferroic system increased with
increasing temperature. The coercive fields and remanent magnetization were higher
over a wide range of temperatures in 10% Gd-Ti co-doped Bi0.9Gd0.1Fe0.9Ti0.1O3
sample compared to those of other compositions. The magnetization versus applied
magnetic field (M-H) hysteresis loops at different temperatures exhibited an
asymmetric shift towards the magnetic field axes which indicated the presence of
exchange bias effect in this material system. The hysteresis loops were also carried
out at temperatures 150 K and 250 K by cooling down the sample from 300 K in
various cooling magnetic fields. The exchange bias fields increased with cooling
magnetic fields and decreased with temperature. The biasing fields were tunable by
field cooling at temperatures up to 250 K. Additionally, the leakage current density
has been measured to explore its effect on the ferroelectric properties of this
multiferroic system. The outcome of this investigation suggested that the substitution
of 10% Gd and Ti in place of Bi and Fe, respectively, in BiFeO3 significantly
enhances its multiferroic properties. The improved properties of this specific
composition was associated with homogeneous reduced grain size, significant
suppression of impurity phases and reduction in leakage current density which was
further asserted by polarization versus electric field (P-E) hysteresis loop
measurements.
