Magnetic properties of vermiculite intercalation compounds

The magnetic properties of vermiculite (V) intercalated with 3d-transition-metal ions (${\mathrm{Mn}}^{2+}$, ${\mathrm{Co}}^{2+}$, ${\mathrm{Ni}}^{2+}$, and ${\mathrm{Cu}}^{2+}$) as interlayer cations have been studied by measuring the dc magnetic susceptibilities of these compounds. The Landé g factors of the magnetic ions in V with and without water molecules coexisting in the gallery have been analyzed by using crystal-field theory. A substantial decrease in the crystal-field strength has been observed when water is removed from the gallery. ${\mathrm{Mn}}^{2+\mathrm{-}}$V and ${\mathrm{Cu}}^{2+\mathrm{-}}$V are found to be paramagnetic for temperatures down to 2 K regardless of the hydration conditions. Dehydrated ${\mathrm{Co}}^{2+\mathrm{-}}$V and ${\mathrm{Ni}}^{2+\mathrm{-}}$V show signatures of an antiferromagnetic phase transition at a few degrees Kelvin (∼5 and ∼3 K, respectively), whereas they do not exhibit any magnetic ordering while water is present in the gallery.