Charge order and magnetoresistivity in a perovskite family of bismuth based manganites

We exemplify some of the problems in designing novel functional materials with the substitution effects on colossal magnetoresistive (CMR) series CaCu
₃
(Mn
_4-x
Fe
_x
)O
₁₂
(x = 0, 0.5, 1.0) and on the charge order phenomenon in half hole-doped manganites Bi
_0.25
RE
_0.25
Ca
_0.5
MnO
₃
(RE = La, Nd, Ho, Er, Tm) and Bi
_0.5
Ca
_0.5
MnO
₃
(RE = La, Nd, Ho, Er, Tm) Bi
_0.5
Ca
_0.5
MnO
₃
. All the CaCu
₃
(Mn
_4-x
Fe
_x
)O
₁₂
samples are ferromagnetic and show a progressive decrease of Tc, saturation magnetization and Weiss temperatures, as the Fe contents increases, which suggests an increment of the antiferromagnetic interactions at the (Mn,Fe) octahedral sublattice and to a considerable canting of the Fe vs Mn spins. The magnetoresistance also decreases upon Fe-doping. In contrast, the Bi-RE samples remain semiconducting by entering antiferromagnetic state at low temperature and similarly to end members Bi
_0.5
Sr
_0.5
MnO
₃
and Bi
_0.5
Ca
_0.5
MnO
₃
are remarkable for their particularly stable charge order of the e
_g
electrons. Although giving rise to important modifications in the resulting magnetic properties and leading at rather low Fe substitution level to full suppression of charge order in Bi
_0.5
Ca
_0.5
(Mn
_1-x
Fe
_x
)O
₃
the Fe substitution does not induce magnetoresistive effect.