K₂SnCl₆ single crystals doped with Cu were grown by the evaporation of saturated solution. The electron magnetic resonance (EMR) of the Cu²⁺ ion in the crystal has been investigated by using an X-band spectrometer.
The rotation pattern in the crystallographic plane together with spin Hamiltonian parameters of Cu²⁺ ion in K₂SnCl₆:Cu single crystal shows that the local site symmetry of the Cu²⁺ ion is cubic at room temperature. The
calculated spectroscopic splitting factor g of Cu²⁺ impurity ion is 2.1908(±0.0007). The hyperfine constants of Cu²⁺ impurity ion due to the ⁶³Cu and ⁶⁵Cu isotopes in K₂SnCl₆:Cu crystal are 0.83(±0.01)×10⁻⁴ cm⁻¹ and 0.89(±0.01)×10⁻⁴ cm⁻¹, respectively. It turns out that the Cu²⁺ ion substitutes for the K⁺ ion without any nearby charge compensation.