Low-frequency internal friction of La2Cu1−xNixO4+δ oxides

The low-frequency internal friction Q−1 and relative shear modulus M of La2Cu1−xNixO4+δ (0 ≤ x ≤ 1) compounds were measured. For x ≤ 0.005, there are two relaxation internal friction peaks around 200 and 250 K, both due to the hopping of the interstitial O atoms, while the peak located at lower temperature is invisible for 0.015 ≤ x ≤ 1. The 3D ordering process of interstitial oxygen occurs at x ≈ 0.5 (δ ≈ 0.082) and the fraction of the 3D ordering phase increases as a function of Ni content.