Negative magnetoresistance effect in Ba-doped layered double perovskite La2CuSnO6

The layered double perovskite La2-xBaxCuSnO6 (0.05 <= x <= 0.20) ceramics were synthesized successfully by solid-state reaction, and the crystal structure, transport and magnetic properties are investigated. It is found that the temperature-dependent resistivity rho(T) shows a semiconductor behavior, which is related to magnetic ordering in two-dimensional CuO2 layers, and the MR effect exists in La2-xBaxCuSnO6. With decreasing the temperature, the MR effect changes from positive to negative, giving a positive maximum at Tmax (approximate to TC) and showing a large negative MR effect at around 40 K with a value of about 20-30% under field H = +/- 50 kOe. It is suggested that the negative MR effect in Ba-doped La2CuSnO6 is attributed to the field-induced suppression of inplane spin-disorder scattering in CuO2 layers. A small amount of Ba doping can adjust the competition and synergy of the AFM and FM interactions through changing the tilt and distortion of CuO6 octahedrons, the inplane Cu-O bond lengths, and the content of Jahn-Teller exciton Cu2+ ions, besides the stabilization of the La2CuSnO6 structure. The competition and synergy of the AFM and FM interactions CuO2 layers dominate the transport and magnetic properties of Ba-doped La2CuSnO6.