Ferromagnetic ordering temperature and internal pressure in manganites La0.7Ca0.3−xSrxMnO3

Lanthanum manganites La0.7Ca0.3−xSrxMnO3 were synthesized and investigated. The jump of Tc at the magnetic ordering temperature dependence on concentration at x=0.15 was revealed. The structural phase transition from the orthorhombic phase (x<0.15) to the rhombohedral one (x≥0.15) corresponds to that concentration. Substitution of Ca2+ ion by Sr2+ leads to the increasing of the average ionic radius in A position (position of La, Ca, Sr) and plays the role of internal pressure. The revealed temperature Tc jump shows that the effect of internal pressure depends on the crystal structure of manganites.