Effect of Tb 3+ doping in mixed-valence manganites and cobaltites.

The magnetic ordering of four Tb3+ -doped manganites and cobaltites, La0.7 Tb0.1 Sr0.2 MnO3 , La0.7 Tb0.1 Ca0.2 MnO3 , La0.7 Tb0.1 Sr0.2 CoO3 and La0.7 Tb0.1 Ca0.2 CoO3 , have been studied by means of neutron diffraction and SQUID magnetometry. All the samples were prepared by sintering of sol-gel precursors and their orthorhombic or rhombohedral perovskite structures at room and low temperatures were refined. A long-range ferromagnetic (FM) order was detected at the Mn and Co sites. In addition, a small but significant ordered moment was observed at A sites of studied cobaltites, which was attributed to local Tb3+ moments, aligned by exchange interactions due to FM ordered Co sublattice. No or minor Tb3+ contribution was detected in studied manganites.