Effect of Jahn–Teller ion in zinc sodium sulphate hexahydrate: a case of low hyperfine coupling constant for Cu(II) ion

Abstract

Single crystal electron paramagnetic resonance (EPR) studies of Cu(II) doped zinc sodium sulphate hexahydrate are carried out from room temperature (RT) to 123 K. The RT spectra show unresolved hyperfine lines and hence angular variation studies are also carried out at 123 K to obtain spin Hamiltonian parameters. The spin Hamiltonian parameters calculated from the 123 K spectra are: g 11=2.039; g 22=2.232; g 33=2.394; A 11=5.64 mT; A 22=4.20 mT; and A 33=7.94 mT. The g-matrix values at RT and 123 K have matched fairly well with each other. The low hyperfine value (A 33), obtained at 123 K, has been explained by considering considerable admixture of ground state with excited state and the delocalization of the unpaired spin density onto the ligands. The admixture coefficients of ground state wave function are: a=0.346, b=0.935, c=0.055, d=0.040, e=−0.040, where a and b correspond to admixture coefficients for and , respectively. Angular variation of Cu(II) resonances in the three orthogonal axes shows that the impurity has entered a substitutional site in the host lattice in place of Zn(II). Bonding parameters, κ=0.295, P=245.4×10−4, α2=0.709,α=0.8421 and α′=0.6034, have also been calculated to fully characterize the EPR.