Etude spectroscopique des ions cuivre (II) en coordinence tétraédrique dans les silicates synthétiques de type milarite
ESR spectra of copper-containing silicates Na 2Mg 5- xCu xSi 12O 30 with a milarite structure have been recorded at two frequencies (X band and Q band) and at several temperatures in the range 298-77K. For x less than 0.5 the well-resolved powder spectrum is characteristic of tetrahedral copper ions in orthorhombic symmetry with gzz = 2.517; gxx = 2.135; gyy = 2.091. The hyperfine structure is completely resolved at 77K ( Azz = 45.9 × 10 -4cm -1; Ayy = 23.0 × 10 -4cm -1; Axx = 41.0 × 10 -4cm -1). The ESR parameters may be interpreted in terms of an admixture of 4 pz wavefunction into the 3 dxy ground state. The results are in good agreement with diffuse reflectance spectra and crystal field calculations.