Spin decoherence processes in the S=1/2 scalene triangular cluster (Cu₃(OH))

We report the synthesis and magnetic properties of the molecular cluster Cu₃(μ₃−OH)(μ-OH)(μ-O₂Ar^4F-Ph)₂(py)₃(OTf)₂, abbreviated as (Cu₃(OH)). Using magnetization, electron paramagnetic resonance and spin dimer analysis, we derive a microscopic magnetic model of (Cu₃(OH)) and measure the electron T₁ and T₂ relaxation times. The Cu²⁺ ions are arranged to form a distorted triangular structure with the three different exchange coupling constants J₁ = −43.5 K, J₂ = −53.0 K, and J₃ = −37.7 K. At T = 1.5 K T₁ is of the order of 10⁻⁴ s and T₂ is evaluated to be 0.26 μs. We find that the temperature dependence of 1/T₁ and 1/T₂ is governed by Orbach process and spin bath fluctuations, respectively. We discuss the role of spin–phonon mechanism in determining a spin decoherence time in a class of spin triangular clusters.