Effects of Ti addition on the magnetic, transport and magnetoresistive properties of La0.67Ca0.33MnO3

La0.67Ca0.33MnO3 (LCMO) fine powder was prepared by a sol-gel procedure. The effects of Ti addition in LCMO on the magnetic, transport and magnetoresistive (MR) properties have been studied systematically. With increasing Ti addition, the magnetization and Curie temperature for the samples decrease monotonously, and the resistivity increases dramatically. The MR effect increases first and then decreases after a maximum MR ratio is reached. When the amount of Ti addition is 5.5% (molar ratio), a maximum MR ratio as large as 500% in 10 kOe at 120 K was obtained, which is 25 times larger than that obtained by the undoped LCMO. The effect of Ti addition is to introduce local magnetic inhomogeneity and inducing spin clusters in the material. Fitting the experimental results to the Brillouin function proposed by Wagner et al. indicates that a possible explanation for the MR behaviour in the Ti-doped LCMO is the formation of spin clusters