Magnetic cluster behavior of α-LiFeO2 related to the cation arrangements

Abstract

In transmission electron microscopy of α-LiFeO2, we found electron diffraction patterns of both cubic structure (a = 4.2 Å) and doubled unit cell structure (a = 8.3 Å) with wavy shaped diffuse scattering due to short-range ordering of Li- and Fe3+ ions. An unusual magnetic state with coexistence of phenomena related to magnetic ordering and glassy behavior in the ac and dc susceptibilities was observed for α-LiFeO2. The bifurcation point was ≈90 K, and the temperature of a broad maximum in the zero-field cooled susceptibility was ≈40 K. Below ≈90 K, the field cooled susceptibility increased monotonically and the zero-field cooled susceptibility deviated below the field cooled one with lowering the temperature. The in-phase ac susceptibility demonstrated a cusp at ≈90 K with a broad shoulder around 60 K. The third harmonic nonlinear susceptibility showed no sharp peak below 200 K. Observed magnetic behavior of α-LiFeO2 can be understood as formation of ferromagnetic clusters, with short-range ordering of Fe3+ spins within the clusters, and progressive freezing of the clusters. The unusual glassy behavior is due to the short-range ordering of cubic structure in α-LiFeO2.