Concentration dependant ferromagnetic metallic to ferromagnetic insulating transition in low doped manganites La0.875Sr0.125-xCaxMnO3 (0 ≤ x ≤ 0.125)

The relationship between structural, transport and magnetic properties with the lattice effect due to replacement of larger Sr2+ ions with smaller Cd2+ ions is reported in the La0.875Sr0.125-xCaxMnO3 system. A transition from R3-bar c to Pnma symmetry is found in the samples with x ≥ 0.0625. Al compounds exhibit a paramagnetic-ferromagnetic phase transition at Tc (Curie temperature) which decreases as x increases. The insulator to metal transition temperature TMI, decreases with increasing Ca content, agreeing with the corresponding Tc decrease. These results have been explained as the consequence of the reduction of the average ionic radius of the A-site element , weakening of double exchange and narrowing of bandwidth. This induces a transition from ferromagnetic metal to ferromagnetic insulator. (author)