Electron Spin Decoherence Dynamics in Magnetic Manganese Hybrid Organic–Inorganic Crystals: The Effect of Lattice Dimensionality

Organic-inorganic metal hybrids with their tailorable lattice dimensionality and intrinsic spin-splitting properties are interesting material platforms for spintronic applications. While the spin decoherence process is extensively studied in lead- and tin-based hybrids, these systems generally show short spin decoherence lifetimes, and their correlation with the lattice framework is still not well-understood. Herein, we synthesized magnetic manganese hybrid single crystals of (4-fluorobenzylamine)₂MnCl₄, ((R)-3-fluoropyrrolidinium)MnCl₃, and (pyrrolidinium)₂MnCl₄, which represent a change in lattice dimensionality from 2D and 1D to 0D, and studied their spin decoherence processes using continuous-wave electron spin resonance spectroscopy. All manganese hybrids exhibit nanosecond-scale spin decoherence time τ₂ dominated by the symmetry-directed spin exchange interaction strengths of Mn²⁺-Mn²⁺ pairs, which is much longer than lead- and tin-based metal hybrids. In contrast to the similar temperature variation laws of τ₂ in 2D and 0D structures, which first increase and gradually drop afterward, the 1D structure presents a monotonous rise of τ₂ with the temperatures, indicating the strong correlation of spin decoherence with the lattice rigidity of the inorganic framework. This is also rationalized on the basis that the spin decoherence is governed by the competitive contributions from motional narrowing (prolonging the τ₂) and electron-phonon coupling interaction (shortening the τ₂), both of which are thermally activated, with the difference that the former is more pronounced in rigid crystalline lattices.