EPR and optical absorption spectral studies on Mn2+ ions doped in potassium thiourea bromide single crystals

EPR and optical absorption spectra of Mn2+ ions doped in potassium thiourea bromide (KTB) single crystals have been studied. The EPR spectrum at room temperature exhibits an isotropic sextet hyperfine pattern which is characteristic of Mn2+ ions. EPR spectra have been studied at different temperatures from 123 to 295 K. The EPR spectra clearly demonstrate that, thiourea plays an important role in modifying the properties of crystal lattices which is expected due to the ferroelectric behavior of thiourea molecule in the complexes. In the temperature range studied, at ∼243 K, a sudden change in the EPR spectrum is observed and the temperature dependant EPR spectra are discussed in this model compound K[CS(NH2)2]4Br. The optical absorption spectrum at room temperature exhibits bands characteristic of Mn2+ ions in an octahedral symmetry. From the observed UV-VIS absorption spectrum, the crystal field splitting parameter Dq and the Racah inter-electronic repulsion parameters B and C have been evaluated and discussed accordingly. The infrared spectrum confirms the composition of several functional group vibrations of O-H, C-S and C-N of PTB crystal lattice.