Structural, transport, and magnetic properties in the Ti-doped manganites LaMn1−xTixO3 (0≤x≤0.2)

The magnetism and transport properties of the samples LaMn1−xTixO3 (0≤x≤0.2) were investigated. All samples show a rhombohedral structure (R3¯C) at room temperature. The sample with x=0 undergoes the paramagnetic-ferromagnetic (PM-FM) transition accompanied by an insulator-metal (I-M) transition due to the oxygen excess. The doped samples show ferromagnetism and cluster behavior at low temperatures. Though no I-M transition associated with the PM-FM transition appears, the magnetoresistance (MR) effect was observed especially at low temperatures under the applied fields of 0.5 T. Due to the fact that the oxygen content in the Ti-doped samples is nearly stochiometry (3.01) and the Hall resistivity at room temperature is negative, the ferromagnetism in LaMn1−xTixO3 (0.05≤x≤0.2) is believed to be consistent with the Mn2+-O-Mn3+ double exchange (DE) mechanism. These results suggest that DE can be obtained by direct Mn-site doping.