Structural, transport, and magnetic properties in the Ti-doped manganites LaMn 1− xTi xO 3 (0≤ x≤0.2)

Abstract

The magnetism and transport properties of the samples LaMn 1− x Ti x O 3 (0≤ x≤0.2) were investigated. All samples show a rhombohedral structure ( R 3 ¯ 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 LaMn 1− x Ti x O 3 (0.05≤ x≤0.2) is believed to be consistent with the Mn 2+–O–Mn 3+ double exchange (DE) mechanism. These results suggest that DE can be obtained by direct Mn-site doping.