Structure, Magnetic, and Electrical Properties of La2NiO 4+\delta Compounds.

We have investigated the structure, magnetic, and electrical properties, and the resistance switching effect (RSE) of La2NiO $_{{ {4+\delta }}} compounds with different excess oxygen levels of \delta = 0.004 - 0.031 . Our results showed the structure changes from tetragonal I4/mmm to orthorhombic Fmmm when reducing \delta value from 0.011 to 0.006. The M(H) curves measured at several temperatures exhibit a coexistence of the weak ferromagnetic and antiferromagnetic interactions. Two shoulders on M(T) curves related to the spin and charge ordering have also been observed. These ordering temperatures depend strongly on \delta ) and low ( RL ) values. The resistance change ratio of the samples defined as 100% \times [RH - RL]/RL is found to be about 18%–57%, which depends on the value of $\delta $ in the samples. [ABSTRACT FROM AUTHOR]