Negative magnetoresistance effect in Ba-doped layered double perovskite La2CuSnO6

The layered double perovskite La _2-xBa _xCuSnO ₆ (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 ρ(T) shows a semiconductor behavior, which is related to magnetic ordering in two-dimensional CuO ₂ layers, and the MR effect exists in La _2-xBa _xCuSnO ₆. With decreasing the temperature, the MR effect changes from positive to negative, giving a positive maximum at T _max (≈ T _C) 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 La ₂CuSnO ₆ is attributed to the field-induced suppression of in-plane spin-disorder scattering in CuO ₂ 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 CuO ₆ octahedrons, the in-plane Cu-O bond lengths, and the content of Jahn-Teller exciton Cu ²⁺ ions, besides the stabilization of the La ₂CuSnO ₆ structure. The competition and synergy of the AFM and FM interactions CuO ₂ layers dominate the transport and magnetic properties of Ba-doped La ₂CuSnO ₆.