Range of existence of the low-symmetry phase of an MgSiF6.6H2O crystal inferred from Mn2+ ESR data at high pressures

An ESR investigation of Mn 2+ :MgSiF 6 . 6H 2 O has revealed characteristics of a low-symmetry phase of this compound. It is shown that axial stresses are reduced at low temperatures and stresses of lower symmetry are increased. There is a considerable reduction in the angle of rotation of the water octahedra within one unit cell. All the parameters of the spin Hamiltonian are determined at temperatures 297, 77, and 4.2 K. A wide range of coexistence of the low- and high-symmetry phases is observed under hydrostatic compression