Magnetic interactions in layered LiNiO2 revealed by EPR of Ni3+

EPR has been used for elucidating the magnetic interactions in layered LiNiO2 with an α-NaFeO2 structure. It has been shown that LiNiO2 belongs to two-dimensional Heisenberg ferromagnetics. Below 30 K, the spin symmetry of the exchange interactions changes from n = 3 (Heisenberg model) to n = 2 (XY model) due to the Jahn-Teller effect for low-spin Ni3+ in a D3d crystal field. From a comparative analysis of the EPR spectra of LiNiO2 (a magnetically concentrated oxide) and LiNixCo1−xO2 (0.1 ⩽ x ⩽ 0.4, magnetically diluted oxides) it is established that the Jahn-Teller effect does not depend on the nickel content in the oxides investigated.