Manifestation of the Jahn–Teller effect in the EPR spectrum of the metalorganic complex [Cu(en)2H2O]SO4

Abstract

The temperature dependence of the resonance spectrum of [Cu(en)2H2O]SO4 single crystals is investigated in the temperature range 2.3–60 K at a frequency of ∼73 GHz. At a temperature T>15 K the angular dependence of the spectrum is described by a spin Hamiltonian of axial symmetry. At T<15 K a lowering of the symmetry to rhombic and a splitting the resonance line for a field orientation H∥b are observed. These effects are discussed in a model of two nonequivalent Jahn–Teller centers with intercoupled dynamic distortions in the cell. The low-temperature behavior of the resonance line is due to critical broadening in the region of short-range magnetic order.