Effect of lattice defects in divalent lattices by incorporating trivalent ions in biominerals: An EPR study of Cr(III) in zinc(II) potassium phosphate hexahydrate

In order to understand the effect of charge compensating vacancies on the number, orientation and magnitude of D‐tensors, single crystal EPR measurements have been carried out with Cr(III) in zinc(II) potassium phosphate hexahydrate at room temperature. During crystal rotations, a maximum of 6/7 resonance lines or a minimum of 2 is noticed. Crystal rotations done in the three orthogonal planes have yielded spin Hamiltonian parameters for one site with: g_xx=1.969, g_yy= 1.995, g_zz= 2.107; D_xx= 66.2 mT; D_yy= 91.7 mT, and D_zz=‐157.9 mT. The powder EPR spectrum indicates a very broad line at g = 8, without any extra resonances from 0 to 650 mT both at room temperature and 77 K. The reason may be that due to large zero field splitting, the resonance at g = 2 is shifted to g = 8 position and the other resonances are below 0 or above 650 mT. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)