Complex δ-dependence of electrical and magnetic properties of La2NiO4+δ

A complex behaviour of La2NiO4+δ with oxygen doping has been studied by resistivity, magnetic susceptibility and ESR measurements. Resistivity data have been achieved in the temperature range 4-1000 K with 0≤δ≤0.17: anomalies connected with a phase separation or a new structural order are observed. ESR spectra [95≤T(K)≤300] show a strong change of line shape when δ≥0.11 where stripe order establishes. Comparison of X-band and Q-band suggests the presence of local fields. Below room temperature, the temperature dependence of ESR line for δ=0.11 may be connected with spin correlation in stripes. The magnetic susceptibility data [300≤T(K)≤1200] show an anomaly at 640 K associated with a disappearance of a ferro-ferrimagnetic contribution the origin of which is associated with hole doping. (orig.)