EPR and IR spectral studies on Mn ions in nickel maleate tetrahydrate single crystals

Electron paramagnetic resonance (EPR) studies have been carried out on Mn²⁺ ions doped in nickel maleate tetrahydrate single crystals in the temperature range 103-413 K on X-band frequency. The EPR spectrum at room temperature exhibits a group of five fine structure transitions each splits into six hyperfine components. Angular variation studies reveal the presence of a single site and it is found that Mn²⁺ ions enter the lattice substitutionally. From the observed EPR spectrum, the spin-Hamiltonian parameters have been evaluated. The variation of zero-field splitting parameter (D) with temperature is measured. The observed EPR spectra exhibit a large anisotropy in the widths of Mn²⁺ resonance lines. The widths of Mn²⁺ resonance lines increase with the Zeeman field intensity and these observations have been discussed in detail. The infrared spectrum exhibits bands characteristic of the carboxylic acid salts.