Paramagnetic properties of the spinel-type Al1−xMnx-sulphate salts for its pillared intercalation into a clay mineral Original Research Article

Paramagnetic interactions on Manganese ions substituted for Aluminium ions by x-mole fraction (x=0.01–0.1) for the spinel-type Al-complexes, [AlO4Al12(OH)24(H2O)12]7+, were investigated. The superconducting quantum interference detection (SQUID) measurements showed a small susceptibility of the order of 10−6 emu/g originated from the Mn ion, and from the saturation value of the DC-magnetization for the 10 mol% Mn concentration, the spin S-value was determined as 2.8 close to its divalent state spin 5/2. The 9 GHz electron paramagnetic resonance (EPR) study revealed that the number of Mn2+ ions embedded in the axial crystal field had a characteristic maximum at the stoichiometric molar concentration Al/(Al+Al12) equal to 7.69%, and the Infrared absorption (IR) experimental result verified this evidence. A theoretical approach was made separately for the concentrations below and above 7.69%. The higher-frequency 24 and 97 GHz EPR measurements examined effectively the result of the crystal field analysis in the 9 GHz, except for the small line splittings due to the higher-order Zeeman and hyperfine effects of the S-state ion. The intercalation of Al1−xMnx-sulphate (x=0.07) as a pillaring agent into a clay mineral, montmorillonite, was confirmed from the X-ray diffraction results.