Measurements of the magnetic susceptibility χ of nonsuperconducting (La1-χSrχ)2NiO4 (LSNO) with χ close to 0.5 between 5 and 700 K revealed the presence of a broad peak in the temperature dependence of χ as observed in superconducting (La1-χSrχ)2CuO4 (LSCO). The broad peak is attributed to the two-dimensional antiferromagnetic (2DAF) correlation between S = 1 2 spins of Ni3+ in the low-spin state. However, contrary to LSCO, the peak temperature, Tmax, which is related to the correlation energy J, increases with χ for LSNO. In LSNO eg electrons are distributed to the 3dx2-y2 and 3dz2 orbitals, both of which are not completely occupied. A strong 2DAF correlation exists among Ni3+ spins in a (3dx2-y2)1 configuration. With increasing χ, the fraction of Ni3+ ions in the (3dx2-y2)1 configuration increases and the effective J increases. This overlap of the orbital levels appears to play an important role in the absence of superconductivity in LSNO.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering