Highly electron-doped cobaltites of the system ${\mathrm{La}}_{1-x}{\mathrm{Ce}}_x\mathrm{Co}{\mathrm{O}}_3(0.1⩽x⩽0.4)$ are synthesized by the growth of epitaxial thin films using pulsed laser deposition. Ferromagnetic order is observed within the entire doping range with the maximum of the Curie temperature, $T_c$, at $x\approx 0.3$, resulting in a magnetic phase diagram similar to that of hole-doped lanthanum cobaltites. The measured spin values strongly suggest an intermediate-spin state of the Co ions which has been also found in the hole-doped system. However, in contrast to the hole-doped material, where $T_c$ is well above 200 K, we observe a strong suppression of the maximum $T_c$ to about 22 K. This is likely to be caused by a considerable decrease of the $\mathrm{Co}3d-\mathrm{O}2p$ hybridization. The observed intriguing magnetic properties are in agreement with previously reported theoretical results.

• Received 4 March 2005

DOI:https://doi.org/10.1103/PhysRevB.72.014466