Electrical and magnetic properties of La 0.67 Ba 0.33 Mn 1− x (Me) x O 3 perovskite manganites: case of manganese substituted by trivalent (Me = Cr) and tetravalent (Me = Ti) elements

The effects of non-magnetic Ti 4+ substitution on the structural, electrical and magnetic properties of La 0.67 Ba 0.33 Mn 1− x Ti x O 3 (0≤ x ≤0.1) are investigated and compared to those existing in La 0.67 Ba 0.33 Mn 1− x Cr x O 3 (magnetic Cr 3+ ). The structural refinement by the Rietveld method revealed that Ti-doped samples crystallize in the cubic lattice with space group Pm3̅m , while samples with Cr crystallize in the hexagonal setting of the rhombohedral R3̅C space group for identical contents of dopant. The most relevant structural features are an increase of the lattice parameters, of the cell volume and of the inter-ionic distances with increasing Ti doping level. Both series of samples show a decrease of the paramagnetic–ferromagnetic transition temperature when the amount of chromium or titanium increases. Transport measurements show that when increasing the metal doping, the resistivity increases whereas the metallic behavior of the parent compound La 0.67 Ba 0.33 MnO 3 is destroyed. For a substitution higher than 5 at.