High pressure and high magnetic field tuning of the S = 1 quantum antiferromagnet system*

[Ni(HF₂)(pyz)₂]SbF₆ is a quasi-one-dimensional S = 1 antiferromagnet in which the magnetic ground state can be tuned by changing the single-ion anisotropy (D) and the intrachain (J ) and interchain (J’) exchange interactions, allowing exploration of the Haldane phase diagram close to quantum criticality. With a newly developed pressure cell designed for pulsed magnetic fields of up to 100 T, we tune the above interactions in [Ni(HF₂)(pyz)₂]SbF₆ using hydrostatic pressures of up to 5.4 GPa. The characteristic form of the magnetic susceptibility was measured in pulsed fields of up to 65 T using a Proximity Detector Oscillator (PDO), allowing values of D, J and J’ to be inferred at each pressure.