EPR studies of Mo3+ ion in single crystals of NH4Al(SO4)2⋅12H2O

Abstract

Electron paramagnetic resonance studies of Mo³⁺ ion in NH₄Al(SO₄)₂⋅12H₂O single crystals are made at X‐band frequencies and at room temperature. It is found that there are four magnetically inequivalent complexes of Mo³⁺ ion in the lattice which exhibit tirgonal symmetry. The angular variation of the fine structure lines is studied in the crystallographic (111) and (100) planes. The z axes of the complexes are found to be along the (111) directions. The spectra are analyzed using the fine structure spin‐Hamiltonian and the parameters are found to be g_∥=1.974, g_⊥=2.009, and D=506.8×10⁻⁴ cm⁻¹. Paramagnetic resonance of the polycrystalline samples is also studied and the usual spin‐Hamiltonian analysis is made. A model is proposed for the position of the Mo³⁺ ion in the lattice of ammonium alum.