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 pressureinduced 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.