Elucidation of site symmetry, location, bond, ground state of Cu2+ ions in lithium sulphate monohydrate single crystal through EPR and optical studies

The highly efficient non linear optical (NLO) lithium suphate monohydrate (LSMH) single crystal with well-developed faces is obtained in a few days by slow evaporation of aqueous solutions at room temperature. Small amount of copper II sulphate pentahydrate is added as the paramagnetic impurity into the system. The powder XRD study shows the monoclinic cell dimension of Cu2+ doped LSMH single crystal. Also FTIR analysis reveals the existence of host in a crystal. The single crystal EPR investigation talks about the presence of copper ion. Even though more than one site is noticed, two are followed and reported. The principle values g and A parameters were calculated for both the sites. The spin Hamiltonian parameters found for both the sites, indicate the rhombic local crystal field symmetry around the impurity ion Cu2+, which is further confirmed by optical absorption studies. Interestingly, both the paramagnetic ions enter the lattice interstitially. The type of bonding between the metal ligand bands for site I and site II are found to be moderate ionic and covalent nature. The ground state wave function of both the sites are observed as d(x2-y2), which is also supported by Rache parameter and optical studies. (C) 2019 Published by Elsevier B.V.