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

Published

April 20, 2017

Author(s)

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

Abstract

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 [υ_eff=2.03(7)υ_B] occurs within the [Ni(pyz)₂]²⁺ square planes below a Neel temperature (T_N) 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.

Citation

Physical Review B

Volume

95

Issue

13

Pub Type

Journals

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Keywords

Diffraction, MAgnetism, order

Citation

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], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=922226 (Accessed October 26, 2025)