The two-electron $\mathrm{}\left(2e\right)\mathrm{}$ doped ${\mathrm{Ca}}_{1-x}{\mathrm{Ce}}_x{\mathrm{MnO}}_3$ $(0\mathrm{}<~x<~0.2)$ system was prepared by sol-gel method and investigated by x-ray absorption spectroscopy (XAS), X-ray diffraction, and temperature and field dependent magnetic and transport measurements. The results are compared in detail to the one-electron $\mathrm{}\left(1e\right)\mathrm{}$-doped ${\mathrm{La}}_{1-y}{\mathrm{Ca}}_y{\mathrm{MnO}}_3$ system, facilitated by the analogous $y=1\mathrm{}-2x$ parametrization as ${\mathrm{Ca}}_{\mathrm{}(1+y)/2\mathrm{}}{\mathrm{Ce}}_{\left(1\mathrm{}-y\right)/2\mathrm{}}{\mathrm{MnO}}_3$ $(0.6\mathrm{}<~y<~1.0).$ The XAS results indicate: that the formal valence of cerium is ${\mathrm{Ce}}^{4+},$ thereby validating the charge transfer of $2e$ per doped Ce to Mn. The XAS also shows separate ${\mathrm{Mn}}^{3+}$ and ${\mathrm{Mn}}^{4+}$ spectral components, in dramatic contrast to results on $1e$-doped systems. Low Ce doping $(x=0.025\mathrm{}$ and 0.05) rapidly stabilizes a robust ferromagnetic component in addition to a persistent antiferromagnetic component in the ordered state. Higher Ce doping $(0.075\mathrm{}<~x<~0.20)$ induces a charge/orbital ordering transition that increases with composition to near 255 K. In different composition ranges the magnetoresistance manifests inter-grain-tunneling and a field coupling of the local charge/orbital order parameter mechanisms. The latter mechanism appears to induce a large magnetoresistance, as high as -72%, in ${\mathrm{Ca}}_{0.925}{\mathrm{Ce}}_{0.075}{\mathrm{MnO}}_3.$

• Received 22 September 2000

DOI:https://doi.org/10.1103/PhysRevB.63.224410