EPR Spectra of Ni(BF₄)₂6H₂O between 100 and 300 K

Abstract

EPR spectra of Ni(BF₄)₂6H₂O single crystal were obtained between 100 K and 300 K. An analysis of the spectra indicated a slightly distorted crystal field from the cubic symmetry, with trigonal axis along the c-axis of the crystal. The spin Hamiltonian parameters g_⁄⁄, g_⊥ and D were determined in the above range of temperatures. D varies linearly as D=0.021(1+0.081T) cm⁻¹ probably due to the phonon modulation of the octahedron of the 6H₂O charges. The line-width of the spectra obeys a ΔH_ms=a+bT² law. The quadratic term comes from the spin-lattice relaxation by a two-phonon Raman process and the constant term represents spin-spin interaction contribution. No phase transition was detected and it is likely that this salt is more stable than some other isomorphous compounds where structure transformation was observed.