Theoretical studies of the spin-Hamiltonian parameters and the effects of the temperature and pressure on the zero-field splitting for Ni2+: Zn(BF4)2·6H2O crystal

The spin-Hamiltonian parameters (the g factors g∥, g⊥ and the zero-field splitting D) and the effects of the temperature and pressure on D for Ni2+ ion at the trigonal Zn2+ site in the low- and room-temperature phase of Zn(BF4)2·6H2O crystal are calculated. The calculations are based on the microscopic spin Hamiltonian theory in teams of the diagonalization of the complete energy matrix of 3d8 ions in trigonal symmetry. The crystal-field parameters related to the impurity structure are obtained from the superposition model. Thus, the local trigonal distortion angle θ, the local angular thermal expansion coefficient and local angular compressibility for Ni2+ impurity centers in Zn(BF4)2·6H2O crystal are estimated. The reasonableness of these local values is discussed.