Magnetic Anisotropy in the Co^II-Al^III-nitrate Layered Double Hydroxides with the Co/Al Ratios 2, 3, and 4

It is shown that the difference in the Co ^II and the Al ^III ionic radii and a random distribution of the Co ions in the metal hydroxide layers of layered double hydroxides (LDHs) result in a series of highly distorted Co(OH) ₆ octahedral complexes. The distortions have been modelled by accounting for the Shannon ionic radii of metals and ligands. The energy of the four low lying Kramers doublets and its g-factors were calculated for all the Co-complexes. The statistical distribution of the distorted octahedra types has been shown to vary with cations content. It was found that the g-factors of the lowest Kramers doublets are highly anisotropic with different orientations of their main axes. The calculated broad range of the g-factor distribution is illustrated by the observed anomalies of the low temperature electron paramagnetic resonance response. The impact of the relative cations content n = (1-×)/× = Co ^II /Al ^III on the nanoparticles aspect ratio of the [Co ^II _1-x Al ^III _x (OH) ₂ ] ^x+ (NO ₃ ) ^- _x ·zH ₂ O LDHs has been considered.