Enhancing easy-plane anisotropy in bespoke Ni(II) quantum magnets

Manson, Jamie L.; Manson, Zachary; Sargent, Ashley; Villa, Danielle; Etten, Nicole L.; Blackmore, William P.; Curley, S. P. M.; Williams, Robert C.; Brambleby, Jamie; Goddard, Paul; Ozarowski, Andrew; Wilson, M. N.; Huddart, B. M.; Lancaster, Tom; Johnson, Roger A.; Blundell, Stephen J.; Bendix, Jesper; Wheeler, Kraig A.; Lapidus, Saul H.; Fan, Xing; Birnbaum, Serena M.; Singleton, John

doi:10.1016/j.poly.2020.114379

Cited by 20 publications

(20 citation statements)

References 43 publications

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“…The Ni–F axial bond, for example, has by far the most ionic character and yields a consistently easy-plane magnet in all cases here and for several other materials with NiF 2 N 4 octahedra. 21 At the other end of the scale, we would expect that a NiI 2 N 4 environment would consistently yield an easy-axis anisotropy, as is the case here for NiI 2 (3,5-lut) 4 . The situation for an electronegativity ratio closer to unity is less clear, with NiCl 2 (3,5-lut) 4 exhibiting greater axial elongation and a D that is slightly more positive than that of NiF 2 (3,5-lut) 4 ·2H 2 O, despite the decreased electronegativity ratio.…”

Section: Discussionmentioning

confidence: 56%

“…This is also supported by studies of varying distortions in similar mixed-ligand octahedra. 21 However, predicting how anisotropy energies change between different mixed-ligand materials is necessarily more complex 16 and remains to be fully elucidated.…”

Section: Introductionmentioning

confidence: 99%

“… 32 To overcome this, we have successfully used additional information available from low-temperature, high-field magnetization measurements (namely spin-flop, metamagnetic, and saturation fields) to simultaneously extract J and D in the low-temperature state. 21 , 32 , 33 ESR is highly suited to characterizing the single-ion properties of quantum magnets. In our compounds, the size of the zero-field splitting requires magnetic fields that are higher than can found in commercially available ESR machines.…”

Section: Introductionmentioning

confidence: 99%

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Magneto-structural Correlations in Ni²⁺–Halide···Halide–Ni²⁺ Chains

et al. 2021

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We present the magnetic properties of a new family of S = 1 molecule-based magnets, NiF 2 (3,5-lut) 4 ·2H 2 O and NiX 2 (3,5-lut) 4 , where X = HF 2 , Cl, Br, or I (lut = lutidine C 7 H 9 N). Upon creation of isolated Ni–X···X–Ni and Ni–F–H–F···F–H–F–Ni chains separated by bulky and nonbridging lutidine ligands, the effect that halogen substitution has on the magnetic properties of transition-metal-ion complexes can be investigated directly and in isolation from competing processes such as Jahn–Teller distortions. We find that substitution of the larger halide ions turns on increasingly strong antiferromagnetic interactions between adjacent Ni 2+ ions via a novel through-space two-halide exchange. In this process, the X···X bond lengths in the Br and I materials are more than double the van der Waals radius of X yet can still mediate significant magnetic interactions. We also find that a simple model based on elongation/compression of the Ni 2+ octahedra cannot explain the observed single-ion anisotropy in mixed-ligand compounds. We offer an alternative that takes into account the difference in the electronegativity of axial and equatorial ligands.

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Section: Discussionmentioning

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Magneto-structural Correlations in Ni²⁺–Halide···Halide–Ni²⁺ Chains

et al. 2021

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“…We attribute this behavior to softer pyz-N coordination that makes the M-N bonds more sensitive to Zn-substitution in stark contrast to the stronger ionic M-F bonds that change very little. This mechanism for locally tuning the ligand-field of NiN 4 F 2 , via Zn-substitution of Ni on other lattice sites, represents a new resource in the “tool kit” 11 employed to design and construct bespoke molecular magnets with desirable combinations of J , J ′, and D . The effect could have particular significance in the field of single-ion magnets.…”

Section: Introductionmentioning

confidence: 99%

Controlling Magnetic Anisotropy in a Zero-Dimensional S = 1 Magnet Using Isotropic Cation Substitution

et al. 2021

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The [Zn 1– x Ni x (HF 2 )(pyz) 2 ]SbF 6 ( x = 0.2; pyz = pyrazine) solid solution exhibits a zero-field splitting ( D ) that is 22% larger [ D = 16.2(2) K (11.3(2) cm –1 )] than that observed in the x = 1 material [ D = 13.3(1) K (9.2(1) cm –1 )]. The substantial change in D is accomplished by an anisotropic lattice expansion in the MN 4 (M = Zn or Ni) plane, wherein the increased concentration of isotropic Zn(II) ions induces a nonlinear variation in M-F and M-N bond lengths. In this, we exploit the relative donor atom hardness, where M-F and M-N form strong ionic and weak coordinate covalent bonds, respectively, the latter being more sensitive to substitution of Ni by the slightly larger Zn(II) ion. In this way, we are able to tune the single-ion anisotropy of a magnetic lattice site by Zn-substitution on nearby sites. This effect has possible applications in the field of single-ion magnets and the design of other molecule-based magnetic systems.

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“…So the allowed EPR transitions are not observed at X-(9.5 GHz) or Q-band (35 GHz) frequency and hence require a high field EPR. [43][44][45][46][47] There are only very few Ni(II) complexes with parameter D lesser or equivalent to the energy of X-/Q-band, and the relaxation times (T 1 , T 2 ) are long enough to exhibit fine structures at room temperature. [48][49][50][51][52][53][54] This has allowed performing EPR experiments to attain complete spin Hamiltonian parameters.…”

Section: Introductionmentioning

confidence: 99%

Interpretation of EPR and optical spectra of Ni(II) ions in crystalline lattices at ambient temperature

Kathirvelu

2021

Magnetic Reson in Chemistry

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Many biologically important paramagnetic metal ions are characterized by electron paramagnetic resonance (EPR) spectroscopy to use as spin probes to investigate the structure and function of biomolecules. Though nickel(II) ions are an essential trace element and part of many biomolecules, the EPR properties are least understood. Herein, the EPR and optical absorption spectra measured at 300 K for Ni(II) ions diluted in two different diamagnetic hosts are investigated and reported. The EPR spectrum of a polycrystalline Ni/Mg (3-methylpyrazole) 6 (ClO 4 ) 2 [Ni/MMPC] shows two transitions at X-band frequency ($9.5 GHz), suggesting the zero-field splitting parameter (D) is larger than the resonance field of the free electron (H o ). This incomplete and complex spectrum is successfully analyzed to obtain EPR parameters. The EPR spectrum of the polycrystalline Ni/Zn(pyrazole) 6 (NO 3 ) 2 [Ni/ZPN] shows a triplet spectrum indicating D < H o . A detailed analysis of single-crystal EPR data yielded the spin Hamiltonian parameters. The optical absorption spectra are deconvoluted to understand the symmetry of the coordination environment in the complex.

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Enhancing easy-plane anisotropy in bespoke Ni(II) quantum magnets

Cited by 20 publications

References 43 publications

Magneto-structural Correlations in Ni²⁺–Halide···Halide–Ni²⁺ Chains

Magneto-structural Correlations in Ni²⁺–Halide···Halide–Ni²⁺ Chains

Controlling Magnetic Anisotropy in a Zero-Dimensional S = 1 Magnet Using Isotropic Cation Substitution

Interpretation of EPR and optical spectra of Ni(II) ions in crystalline lattices at ambient temperature

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Enhancing easy-plane anisotropy in bespoke Ni(II) quantum magnets

Cited by 20 publications

References 43 publications

Magneto-structural Correlations in Ni2+–Halide···Halide–Ni2+ Chains

Magneto-structural Correlations in Ni2+–Halide···Halide–Ni2+ Chains

Controlling Magnetic Anisotropy in a Zero-Dimensional S = 1 Magnet Using Isotropic Cation Substitution

Interpretation of EPR and optical spectra of Ni(II) ions in crystalline lattices at ambient temperature

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Magneto-structural Correlations in Ni²⁺–Halide···Halide–Ni²⁺ Chains

Magneto-structural Correlations in Ni²⁺–Halide···Halide–Ni²⁺ Chains