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Combining Microscopic and Macroscopic Probes to Untangle the Single-Ion Anisotropy and Exchange Energies in an S = 1 Quantum Antiferromagnet



Jamie Brambleby, Jamie Lee Manson, Paul A. Goddard, Matthew B. Stone, Roger D. Johnson, Pascal Manuel, Jacquelina A. Villa, Craig Brown, Helen Lu, Shalinee Chikara, Vivien Zapf, Saul H. Lapidus, Rebecca Scatena, Piero Macchi, Yu-Sheng Chen, Lai-Chin Wu, John Singleton


We derive a synergistic approach to determine the spin Hamiltonian and field-temperature phase diagram for polycrystalline samples of S = 1 [Ni(HF2)(pyz)2]SbF6 by exploiting a selected range of experimental techniques. Spatial exchange anisotropy was anticipated along antiferromagnetic (AFM) Ni-FHF-Ni (J) and Ni-pyz-Ni (J') superexchange pathways such that J>J'. Combining magnetization (for fields up to υ0Hless than or equal to} 60 T) with elastic and inelastic neutron scattering (υ0less than or equal to}10 T) allow the single-ion anisotropy energy D and the Heisenberg J and J' spin-exchange interactions to be quantified. Collinear XY-AFM order of the Ni(II) magnetic moments [υeff=2.03(7)υB] occurs within the [Ni(pyz)2]2+ square planes below a Neel temperature (TN) of 12.2 K. From the collective proves, we deduced the parameters; D = 13.3(1) K, J = 10.4(3) K and J'= 1.4(2) K such that D/J (approximately equal to} 1.3 and J'/J approximately equal to}0.1. Applying static magnetic fields up to 10 T induces the moments to cant and a concomitant softening of the spin-wave excitation. Density-functional theory calculations predict similar couplings (J = 9.2 K, J'=1.8 K) with a total spin population of ca. 1.75e residing on the Ni(II) ion while remaining 0.25e is delocalized over both ligand types. The general procedure outlined herein will permit phase boundaries and quantum critical points to be explored. Ultimately, this will foster identification of exotic states of quantum matter, such as a spin liquid, in similar S = 1 materials for which the growth suitable single-crystals remain elusive.
Physical Review B


Diffraction, MAgnetism, order


Brambleby, J. , Manson, J. , Goddard, P. , Stone, M. , Johnson, R. , Manuel, P. , Villa, J. , Brown, C. , Lu, H. , Chikara, S. , Zapf, V. , Lapidus, S. , Scatena, R. , Macchi, P. , Chen, Y. , Wu, L. and Singleton, J. (2017), Combining Microscopic and Macroscopic Probes to Untangle the Single-Ion Anisotropy and Exchange Energies in an S = 1 Quantum Antiferromagnet, Physical Review B, [online], (Accessed June 3, 2023)
Created April 19, 2017, Updated October 12, 2021