Spin-Lattice Coupling in [Ni(HF2)(pyrazine)2]SbF6 Involving the HF2- Superexchange Pathway.

Magnetoelastic coupling in the quantum magnet [Ni(HF2)(pyrazine)2]SbF6 has been investigated via vibrational spectroscopy using temperature, magnetic field, and pressure as tuning parameters. While pyrazine is known to be a malleable magnetic superexchange ligand, we find that HF2- is surprisingly sensitive to external stimuli and is actively involved in both the magnetic quantum phase transition and the series of pressure-induced structural distortions. The amplified spin-lattice interactions involving the bifluoride ligand can be understood in terms of the relative importance of the intra- and interplanar magnetic energy scales.