Enhanced low-field magnetoresistance in LSMO/AZO composites prepared by plasma activated sintering

To improve the low-field magnetoresistance of La0.7Sr0.3MnO3 (LSMO) ceramics, Al (3 wt%)-doped ZnO (AZO) was added to LSMO as the second phase, and (1 − x) LSMO/xAZO (x = 0, 0.1, 0.2, 0.3 and 0.4) composites were first prepared by plasma activated sintering. The effect of the AZO content on the structural, electrical and magnetic properties of the composites was studied. The results of XRD, SEM, EDS and TEM analyses indicated that the LSMO phase coexisted with the AZO phase without any reaction, and that all of the samples had a high relative density (> 96.9%). The magnetization of the (1 − x) LSMO/xAZO composites decreased with the increase of the AZO content, while the Curie temperature remained at approximately 360 K. With an increase of the AZO content, both the resistivity and metal-insulator transition temperatures decreased. The resistivity (ρ) - temperature (T) data were well fitted to the equation of ρ=ρ0+ρ2T2+ρ4.5T4.5+ρ5T5 in the low-temperature region, and to the non-adiabatic small polaron hopping model in the high-temperature region. The maximum value of the low-field magnetoresistance at room temperature was obtained for the 0.8LSMO/0.2AZO composite, which reached 16.2%, indicating the addition of AZO effectively enhanced the low-field magnetoresistance of LSMO ceramics.