Short-range spin correlations in β″ -LiFeO₂ from bulk magnetization, neutron diffraction, and μsR experiments

Bulk magnetization, neutron-diffraction, and muon-spin-rotation/relaxation (μ⁺ SR) measurements have been performed to study magnetic ordering behavior in β″ -LiFeO₂. At room temperature, structural short-range order of Fe atoms was observed with correlation length roughly corresponding to inter-Fe distance. Bulk magnetization, μ⁺ SR and neutron diffraction all suggest that β″ -LiFeO₂ is similar to a superparamagnet in the range 110<T<170 K, possibly due to the formation of small spin clusters attributable to atomic short-range order. At lower temperatures, gradual increase in the muon precession frequency as well as the neutron diffuse scattering intensity were observed below 110 K, indicating development of intercluster correlations. While a bulk magnetic ordering was detected in the μ⁺ SR results, neutron diffraction concludes that the intercluster correlations are definitely short ranged; the correlation length was estimated as ξ_s ≈ 14 Å, which is almost temperature independent.