Comparison of local crystal structure and magnetic properties of cation substituted LiNiO2 compositions

We investigate the change in local crystal structure and its impact on the magnetic ground states of LiNi_0.5X_0.5O₂ (X = Mn, Co) and LiNi_0.75Y_0.25O₂ (Y = Fe, Al) and contrast it against LiNiO₂. The solid-state synthesis route adopted here introduces some anti-site disorder in the final compositions due to the volatile nature of Li ions. Powder X-ray diffraction (XRD) profiles were hence recorded using a rotating anode X-ray source to determine the percentage of anti-site disorder, and phase purity of all the compositions. Rietveld refinement of the XRD profiles confirms the symmetry and provides the estimation of unit cell parameters. Near-edge X-ray absorption spectra verified the oxidation state of various cations present in the compositions. Analysis of the extended X-ray absorption fine structure spectra identify the signatures of Jahn–Teller distortion in Ni³⁺ rich compositions. Changes in NiO₆ octahedral environment has a much deeper impact on the magnetism of these compositions.