Improvements of conductive property and room temperature magnetoresistance in Ag–Ti-added La 0.67Ba 0.33MnO 3

Abstract

Structural, magnetic, electrical, and magnetotransport properties have been carried out on the Ag-added La 0.67Ba 0.33MnO 3/(TiO 2) 0.035 (LBT) (abbreviated by LBT/Ag x ,) composites. Ag addition has little influence on the magnetization or Curie temperature ( T C), but decreases the resistivity ( ρ) and sharps the ρ peak evidently. The ρ in the ferromagnetic (FM) metallic regime is proportional to T 2, reflecting that the conductive mechanism mainly arises from the electron–electron scattering. In the paramagnetic (PM) insulating region, the ρ data fit well to the self-trapped small polaron hopping model. The ρ– T curves for x = 0.27 and 0.30 samples fit well with the phenomenological percolation approach, which is based on the phases segregation of ferromagnetic metallic clusters and paramagnetic insulating regions. These excellent agreements highlight the dominant intrinsic behavior of LBT. In addition, from the magnetotransport measurements, a large magnetoresistance (MR) ratio up to 41% was obtained at 280 K, and 10 kOe for x = 0.27 sample. The good fits between the field dependence of MR and Brillouin function indicate that the MR behavior in the Ag-added LBT is induced by the spin-dependent hopping of the electrons among the spin clusters, and which is related to the increase and growth of the FM spin clusters.