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Hand AT, Watson-Sanders BD, Xue ZL. Spectroscopic techniques to probe magnetic anisotropy and spin-phonon coupling in metal complexes. Dalton Trans 2024; 53:4390-4405. [PMID: 38380640 DOI: 10.1039/d3dt03609j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2024]
Abstract
Magnetism of molecular quantum materials such as single-molecule magnets (SMMs) has been actively studied for potential applications in the new generation of high-density data storage using SMMs and quantum information science. Magnetic anisotropy and spin-phonon coupling are two key properties of d- and f-metal complexes. Here, phonons refer to both intermolecular and intramolecular vibrations. Direct determination of magnetic anisotropy and experimental studies of spin-phonon coupling are critical to the understanding of molecular magnetism. This article discusses our recent approach in using three complementary techniques, far-IR and Raman magneto-spectroscopies (FIRMS and RaMS, respectively) and inelastic neutron scatterings (INS), to determine magnetic excited states. Spin-phonon couplings are observed in FIRMS and RaMS. DFT phonon calculations give energies and symmetries of phonons as well as calculated INS spectra which help identify magnetic peaks in experimental INS spectra.
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Affiliation(s)
- Adam T Hand
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
| | | | - Zi-Ling Xue
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
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Hughey KD, Lee M, Nam J, Clune AJ, O'Neal KR, Tian W, Fishman RS, Ozerov M, Lee J, Zapf VS, Musfeldt JL. High-Field Magnetoelectric and Spin-Phonon Coupling in Multiferroic (NH 4) 2[FeCl 5·(H 2O)]. Inorg Chem 2022; 61:3434-3442. [PMID: 35171587 DOI: 10.1021/acs.inorgchem.1c03311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We combine high field polarization, magneto-infrared spectroscopy, and lattice dynamics calculations with prior magnetization to explore the properties of (NH4)2[FeCl5·(H2O)]─a type II molecular multiferroic in which the mixing between charge, structure, and magnetism is controlled by intermolecular hydrogen and halogen bonds. Electric polarization is sensitive to the series of field-induced spin reorientations, increasing linearly with the field and reaching a maximum before collapsing to zero across the quasi-collinear to collinear-sinusoidal reorientation due to the restoration of inversion symmetry. Magnetoelectric coupling is on the order of 1.2 ps/m for the P∥c, H∥c configuration between 5 and 25 T at 1.5 K. In this range, the coupling takes place via an orbital hybridization mechanism. Other forms of mixing are active in (NH4)2[FeCl5·(H2O)] as well. Magneto-infrared spectroscopy reveals that all of the vibrational modes below 600 cm-1 are sensitive to the field-induced transition to the fully saturated magnetic state at 30 T. We analyze these local lattice distortions and use frequency shifts to extract spin-phonon coupling constants for the Fe-O stretch, Fe-OH2 rock, and NH4+ libration. Inspection also reveals subtle symmetry breaking of the ammonium counterions across the ferroelectric transition. The coexistence of such varied mixing processes in a platform with intermolecular hydrogen- and halogen-bonding opens the door to greater understanding of multiferroics and magnetoelectrics governed by through-space interactions.
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Affiliation(s)
- Kendall D Hughey
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Minseong Lee
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Jisoo Nam
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Korea
| | - Amanda J Clune
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Kenneth R O'Neal
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Wei Tian
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Randy S Fishman
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Mykhaylo Ozerov
- National High Magnetic Field Laboratory, Florida State University, Florida, 32310, United States
| | - JunHee Lee
- School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Korea
| | - Vivien S Zapf
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
| | - Janice L Musfeldt
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States.,Department of Physics, University of Tennessee, Knoxville, Tennessee 37996, United States
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Bikas R, Korabik M, Sanchiz J, Noshiranzadeh N, Mirzakhani P, Gałkowska A, Szeliga D, Kozakiewicz-Piekarz A. Crystal structure and magnetic interactions of a new alkoxido and azido bridged 1D copper(II) coordination polymer. J SOLID STATE CHEM 2021. [DOI: 10.1016/j.jssc.2021.122484] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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Kenny EP, Jacko AC, Powell BJ. Tight-Binding Approach to Pyrazine-Mediated Superexchange in Copper-Pyrazine Antiferromagnets. Inorg Chem 2021; 60:11907-11914. [PMID: 34310131 DOI: 10.1021/acs.inorgchem.1c00532] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We investigate the cause of spatial superexchange anisotropy in a family of copper-based, quasi-two-dimensional materials with very similar geometries. The compounds in this family differ mainly in their inter-layer separation but they have very different magnetic interactions, even within the basal plane. We use density functional theory and Wannier functions to parameterize two complimentary tight-binding models and show that the superexchange between the Cu2+ ions is dominated by a σ-mediated interaction between hybrid Cu-pyrazine orbitals centered on the copper atoms. We find no correlations between the strength of this exchange interaction and homologous geometric features across the compounds, such as Cu and pyrazine bond lengths and orientations of nearby counterions. We find that the pyrazine tilt angles do not affect the Cu-pyrazine-Cu exchange because the lowest unoccupied molecular orbital on pyrazine is at a very high energy (relative to the frontier orbitals, which are Cu-based). We conclude that careful control of the entire crystal structure, including non-homologous geometric features such as the inter-layer organic ligands, is vital for engineering magnetic properties.
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Affiliation(s)
- E P Kenny
- School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - A C Jacko
- School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - B J Powell
- School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland 4072, Australia
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Kirkman-Davis E, Witkos FE, Selmani V, Monroe JC, Landee CP, Turnbull MM, Dawe LN, Polson MIJ, Wikaira JL. Pyrazine-bridged Cu(ii) chains: diaquabis(n-methyl-2-pyridone)copper(ii) perchlorate complexes. Dalton Trans 2020; 49:13693-13703. [PMID: 32996511 DOI: 10.1039/d0dt02716b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A family of pyrazine-bridged, linear chain complexes of Cu(ii) of the formula [CuL2(H2O)2(pz)](ClO4)2 [pz = pyrazine; L = n-methyl-2(1H)-pyridone, n = 3 (1), 5 (2), and 6 (3)] has been prepared. Single-crystal X-ray diffraction shows six-coordinate, pyrazine-bridged chains with trans-pairs of ancillary ligands. The substituted pyridine molecules exist in their pyridone tautomers and are coordinated through the carbonyl oxygen atom. The structure is stabilized by intramolecular hydrogen bonds between the pyridone and water molecule, and via hydrogen bonds between the water molecules and perchlorate ions. 2 undergoes a crystallographic phase transition between C2/c (high temperature phase) and P1[combining macron] (low temperature phase). Powder EPR spectra reveal that all complexes are rhombic, although differences between gx and gy can only be seen clearly at Q-band. Variable temperature magnetic susceptibility data show antiferromagnetic interactions and the data were fit to the uniform chain model yielding J/kB = -9.8, -9.2 and -11 K for 1-3 respectively. Attempts to model an interchain interaction strength indicate that the chains are very well isolated.
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Affiliation(s)
- Emma Kirkman-Davis
- Carlson School of Chemistry and Biochemistry, Clark University, 950 Main Street, Worcester, MA 01610, USA.
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