Ferromagnetic order in the electron-doped system La_1−xCe_xCoO₃

Highly electron-doped cobaltites of the system La_1−xCe_xCoO₃ (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≈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 Co 3d−O 2p hybridization. The observed intriguing magnetic properties are in agreement with previously reported theoretical results.