ESR Study of the Crystallographic Phases in Zn2P2O7:Mn and Zn2P2O7:Cu

Abstract

The ESR spectra of Mn⁺⁺ and Cu⁺⁺ in Zn₂P₂O₇ have been studied between room temperature and 200°C. A first‐order phase transition is found at 132°C and a transition of higher thermodynamic order occurs near 155°C. The space group of Zn₂P₂O₇ above 155°C is determined to be C‐2/m, whereas between 132° and 155°C it is C‐m. The value of | D | in the spin Hamiltonian for Mn⁺⁺ ranges from 612 to 1319 G with nearly isotropic g values. The g values for Cu⁺⁺ indicate an anisotropic environment with nearly axial symmetry about the z axis. The spectral lines of Zn₂P₂O₇:Mn⁺⁺ are broadened near the upper transition with the broadness dependent upon the particular electronic transition involved. This phenomenon is discussed in terms of possible mechanisms for the upper phase transition.