Monometallic complexes of paramagnetic transition metal or lanthanide metal ions have found to exhibit single-molecule magnet (SMM) behaviour with an appreciably enhanced magnetic anisotropy, due to stabilisation of an unquenched orbital moment. The understanding and controlling of their magnetic anisotropy and relaxation dynamics is fundamental for the engineering of better performing single-molecule magnets. Recently a Ni(II)-based single-ion magnet has been found to exhibit an unprecedented magnetic anisotropy. We propose to use MARI spectrometer to directly measure the single ion zero field splitting responsible for the slow relaxation of the magnetization of this new Ni-based single ion magnet. We will also measure the phonon density of states to better understand the detalis of its relaxation of the magnetization.