The substitution of ruthenium for manganese has been studied in the ${\mathrm{Sm}}_{1-x}{\mathrm{Ca}}_x{\mathrm{MnO}}_3$ series, leading to a magnetic (T vs x) phase diagram where a large region of ferromagnetic metallic phases appears. These results are compared with those obtained by chromium doping in the same system, showing the much stronger effect of ruthenium. Other lanthanide series have also been characterized in order to investigate the size effect in the ruthenium doped compounds. A comprehensive magnetic study by powder neutron diffraction has been performed on the ${\mathrm{Sm}}_{0.2}{\mathrm{Ca}}_{0.8}{\mathrm{Mn}}_{0.9}{\mathrm{Ru}}_{0.1}{\mathrm{O}}_3$ compound in connection with the phase separation evidenced by the susceptibility measurements. Finally, models for orbital and spin ordering are proposed to explain the Cr and Ru induced ferromagnetism and metallicity.

• Received 26 July 2000

DOI:https://doi.org/10.1103/PhysRevB.63.174402