MAGNETIC-PROPERTIES OF VERMICULITE INTERCALATION COMPOUNDS

The magnetic properties of vermiculite (V) intercalated with 3d-transition-metal ions (Mn2+, Co2+, Ni2+, and Cu2+) as interlayer cations have been studied by measuring the dc magnetic susceptibilities of these compounds. The Lande 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. Mn2+-V and Cu2+-V are found to be paramagnetic for temperatures down to 2 K regardless of the hydration conditions. Dehydrated Co2+-V and Ni2+-V show signatures of an antiferromagnetic phase transition at a few degrees Kelvin (approximately 5 and approximately 3 K, respectively), whereas they do not exhibit any magnetic ordering while water is present in the gallery.