Magnetic susceptibility of vermiculite intercalation compounds with magnetic ions as intercalants

The dc magnetic susceptibility of vermiculite intercalation compounds (VIC’s), having hydrated ${\mathrm{Ni}}^{2+}$, ${\mathrm{Co}}^{2+}$, ${\mathrm{Mn}}^{2+}$, ${\mathrm{Cu}}^{2+}$, ${\mathrm{Dy}}^{3+}$, and ${\mathrm{Er}}^{3+}$ ions in the interlamellar space between the silicate layers, has been measured in the temperature range between 4.2 and 300 K. The magnetic susceptibilities of these compounds show a Curie-Weiss behavior, with those of ${\mathrm{Co}}^{2+}$, ${\mathrm{Mn}}^{2+}$, and ${\mathrm{Cu}}^{2+}$ being essentially paramagnetic, showing a Curie-Weiss temperature FTHETA close to zero but negative, whereas those of ${\mathrm{Ni}}^{2+}$, ${\mathrm{Dy}}^{3+}$, and ${\mathrm{Er}}^{3+}$ are ferromagnetic. dc susceptibility and thermogravimetric measurement results also show that the magnetic VIC’s have different cation contents, u: (i) the Ni, Co, and Mn VIC’s show incomplete ion exchange (u=0.76±0.08) for Mg (u=0.93), (ii) the Cu VIC contains more cations (u=1.12±0.07) than the Mg parent, suggesting secondary reactions within the intercalate layer probably due to hydrolysis of the ${\mathrm{Cu}}^{2+}$ ion, and (iii) the Dy and Er VIC’s exchange two for three Mg ions as expected for trivalent ions (u=0.60±0.01). The in-plane structure of these VIC’s is discussed in light of a mixed phase formed of possible commensurate structures.