Magnetic Anisotropy in the CoII-AlIII-nitrate Layered Double Hydroxides with the Co/Al Ratios 2, 3, and 4

It is shown that the difference in the ${\mathrm{Co}}^{\mathrm{II}}$ and the ${{\mathrm {Al}}}^{{{\mathrm {III}}}}$ 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)$\epsilon$ 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 $n=(1-x)$/$x={\mathrm{Co}}^{\mathrm{II}}/{\mathrm {{A1}^{{III}}}}$ on the nanoparticles aspect ratio of the ${\mathrm {[{C}{o}^{{I}{I}_{1-{x}}}{A}1^{{I}{I}{I}_{{x}}}({O}{H})_{2}]^{{x}+}({N}{O}_{3})_{{x}}^{-}\cdot {z}{H}_{2}{O}}}$ LDHs has been considered.