It is seen that BDFCO–BTO composite exhibits a better magnetic hysteresis than the undoped BFO
when compared to BDFO–BTO composite. From the M–H curves and
from Table 1, it is observed that the magnetic parameters of BDFCO–
BTO are remarkably better than that of BDFO–BTO composite. BDFO–
BTO shows relatively low saturation compared to BDFCO–BTO composite. M–H curve for BDFCO–BTO composite exhibits an almost
square shape with the maximum coercive field value (Hc) while that
of BDFO–BTO composite is a thin loop and hence it can be concluded
that BDFO–BTO composite shows soft FM while BDFCO–BTO composite reveals the hard FM character. This conspicuous difference is
attributed to the introduction of the nonmagnetic Cu, effective
suppression of spiral spin structure and improved magnetic coupling
in BDFCO–BTO composite [18,19]. The presence of oxygen vacancies
contributes to the magnetization as reported by Yu et al. [20]. Doping
of Cu2 þions not only reduces the formation of Fe2 þ ion but also
controls the Fe2 þ/Fe3 þ charge fluctuation [21]; it also favours the
formation of oxygen vacancies [22]. Therefore, it is clear that Cu doped
at Fe site plays an important role in the creation of oxygen vacancies
and hence contributes to the observed enhanced magnetization. Our
results are found to be better than that of other experimental reports
[12]. This is attributed to the better mechanical coupling between the
components of the composites and due to the presence of dopants Dy
and Cu in BFO.