Magnetic anisotropy in the CoII-AlIII-nitrate layered double hydroxides with the Co/Al ratios 2, 3, and 4

Abstract

It is shown that the difference in the CoII and the AlIII 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-x)/x = CoII/AlIII on the nanoparticles aspect ratio of the [CoII1-xAlIIIx(OH)2]x+(NO3)- x·zH2O LDHs has been considered.