Composition-mediated long-range-order transition from AFM to FM in LixNi2−xO2 solid solutions

A systematic study of the magnetic properties of LixNi2−xO2 solid solutions with the composition 0.40≤x≤0.91 has been performed. The relationship between composition and magnetic properties has been investigated. For 0.40≤x≤0.67, the compounds crystallize in the face-centered-cubic rocksalt structure in which the Ni2+ and Ni3+ ions are randomly distributed, leading to the existence of long-range antiferromagnetic (AFM) order. For 0.67<x≤0.91, the compounds crystallize in the rhombohedral α-NaFeO2-type structure in which the metal ions orderly occupy the lattice positions, resulting in long-range ferromagnetic (FM) order. With increasing Li content, the long-range magnetic order changes from AFM-type to FM-type, which originates from the composition-mediated distribution of Ni2+ and Ni3+ions. The ordering temperature decreases linearly with increasing Li concentration, which is ascribed to the dilution effect of Li substitution..