Molecular Magnets

McInnes, Eric J. L.; Winpenny, Richard E. P.

doi:10.1016/b978-0-08-097774-4.00419-8

Cited by 9 publications

(11 citation statements)

References 275 publications

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“…Spin–phonon coupling, often called spin–lattice relaxation, is the most prevalent mechanism of magnetic relaxation in SMMs. ,,,,− The coupling of phonons to excited crystal-field states in lanthanide complexes may well lead to additional methods of relaxation. These spin–phonon interactions, including their nature and magnitude, are still not clearly understood.…”

Section: Introductionmentioning

confidence: 99%

Inter-Kramers Transitions and Spin–Phonon Couplings in a Lanthanide-Based Single-Molecule Magnet

et al. 2020

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Spin–phonon coupling plays a critical role in magnetic relaxation in single-molecule magnets (SMMs) and molecular qubits. Yet, few studies of its nature have been conducted. Phonons here refer to both intermolecular and intramolecular vibrations. In the current work, we show spin–phonon couplings between IR-active phonons in a lanthanide molecular complex and Kramers doublets (from the crystal field). For the SMM Er[N(SiMe3)2]3 (1, Me = methyl), the couplings are observed in the far-IR magnetospectroscopy (FIRMS) of crystals with coupling constants ≈ 2–3 cm–1. In particular, one of the magnetic excitations couples to at least two phonon excitations. The FIRMS reveals at least three magnetic excitations (within the 4 I 15/2 ground state/manifold; hereafter, manifold) at 0 T at 104, ∼180, and 245 cm–1, corresponding to transitions from the ground state, M J = ±15/2, to the first three excited states, M J = ±13/2, ±11/2, and ±9/2, respectively. The transition between the ground and first excited Kramers doublet in 1 is also observed in inelastic neutron scattering (INS) spectroscopy, moving to a higher energy with an increasing magnetic field. INS also gives complete phonon spectra of 1. Periodic DFT computations provide the energies of all phonon excitations, which compare well with the spectra from INS, supporting the assignment of the inter-Kramers doublet (magnetic) transitions in the spectra. The current studies unveil and measure the spin–phonon couplings in a typical lanthanide complex and throw light on the origin of the spin–phonon entanglement.

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Section: Introductionmentioning

confidence: 99%

Inter-Kramers Transitions and Spin–Phonon Couplings in a Lanthanide-Based Single-Molecule Magnet

et al. 2020

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“…All electronic structure calculations were performed on the X-ray crystal structure data using ORCA 4.2.1 code. 92,93 We have employed a complete active space selfconsistent field (CASSCF) 94 with a minimal active space comprised of seven d-electrons in five active d-orbitals, i.e., CAS (7,5) for complex 1. Scalar relativistic effects were incorporated employing the Douglas− Kroll−Hess (DKH) approximation.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…Single-molecule magnets (SMMs) with slow spin relaxation from one ground state to another have been actively studied as potential new data storage materials. − Ideally, the primary relaxation mechanism would be to traverse the energy barrier separating the two states. ,− However, other processes, such as spin–lattice relaxations (i.e., spin–phonon coupling) and quantum tunneling, often complicate the relaxation processes. − These mechanisms are still poorly understood. In addition, direct determination of the barrier height is essential.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive Studies of Magnetic Transitions and Spin–Phonon Couplings in the Tetrahedral Cobalt Complex Co(AsPh₃)₂I₂

et al. 2022

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A combination of inelastic neutron scattering (INS), far-IR magnetospectroscopy (FIRMS), and Raman magneto-spectroscopy (RaMS) has been used to comprehensively probe magnetic excitations in Co(AsPh 3 ) 2 I 2 (1), a reported singlemolecule magnet (SMM). With applied field, the magnetic zero-field splitting (ZFS) peak (2D′) shifts to higher energies in each spectroscopy. INS placed the ZFS peak at 54 cm −1 , as revealed by both variable-temperature (VT) and variable-magnetic-field data, giving results that agree well with those from both far-IR and Raman studies. Both FIRMS and RaMS also reveal the presence of multiple spin−phonon couplings as avoided crossings with neighboring phonons. Here, phonons refer to both intramolecular and lattice vibrations. The results constitute a rare case in which the spin− phonon couplings are observed with both Raman-active (g modes) and far-IR-active phonons (u modes; space group P2 1 /c, no. 14, Z = 4 for 1). These couplings are fit using a simple avoided crossing model with coupling constants of ca. 1−2 cm −1 . The combined spectroscopies accurately determine the magnetic excited level and the interaction of the magnetic excitation with phonon modes. Density functional theory (DFT) phonon calculations compare well with INS, allowing for the assignment of the modes and their symmetries. Electronic calculations elucidate the nature of ZFS in the complex. Features of different techniques to determine ZFS and other spin-Hamiltonian parameters in transition-metal complexes are summarized.

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“…Single-molecule magnets (SMMs) exhibit slow relaxation of their magnetization, a desired property in retaining the information stored, − with potential applications in, e.g., molecular spintronics and high-density information storage. One current focus of the SMM research is mononuclear complexes containing one metal ion (SIMs).…”

Section: Introductionmentioning

confidence: 99%

Advanced Spectroscopic and Computational Studies of a Cobalt(II) Coordination Polymer with Single-Ion-Magnet Properties

et al. 2022

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Two-dimensional (2D) coordination polymer (CP) [Co III (CN) 6 ] 2 [Co II (TODA)] 3 •7H 2 O (TODA = 1,4,10-trioxa-7,13diazacyclopentadecane, Co-TODA) was reported earlier to show field-induced slow magnetic relaxation, displaying single-ion magnet (SIM) behaviors. Most SIMs are molecular compounds with fewer adopting coordination polymer (CP) or metal−organic framework (MOF) structures. In the current work, magnetic and phonon properties of Co-TODA have been studied by advanced spectroscopies and computations. The combined use of far-IR magneto-spectroscopy (FIRMS) and variable-temperature (VT) high-frequency and -field electron paramagnetic resonance (HFEPR) gives spin Hamiltonian (SH) parameters: Axial zerofield splitting (ZFS) parameter D as +38.0(1.0) ≤ D ≪ +40.2(1.0) cm −1 and rhombic ZFS parameter E as 0 ≪ |E| ≤ 7.3(1.0) cm −1 , showing that Co-TODA has the easy-plane magnetic anisotropy. Two Co II centers in the CP, as determined by synchrotron single-crystal X-ray diffraction at 15(2) K, show similar magnetic properties indistinguishable in FIRMS at 5.3(3) K or in HFEPR at 5−150 K. Ab initio calculations explore the origin of the magnetic anisotropy and magnetostructural correlations. VT inelastic neutron scattering (INS) spectra of Co-TODA have been obtained to show the phonon properties of the CP. Density functional theory (DFT) calculations, giving both a calculated INS spectrum and spin distributions in Co-TODA, demonstrate that, compared with other high-spin Co II complexes, the larger the spin density on a metal ion, the larger the ZFS in the complex. Pulsed X-band EPR studies probe relaxations of the Co II ions from the M S = +1/2 to −1/2 state in the ground Kramers doublet (KD), yielding spin−lattice (T 1 ) and spin−spin relaxation (T 2 ) times. The work reported here highlights the versatility and power of the spectroscopic techniques and computations in the characterization of magnetic and phonon properties of a CP and the understanding of its magnetic anisotropy.

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Molecular Magnets

Cited by 9 publications

References 275 publications

Inter-Kramers Transitions and Spin–Phonon Couplings in a Lanthanide-Based Single-Molecule Magnet

Inter-Kramers Transitions and Spin–Phonon Couplings in a Lanthanide-Based Single-Molecule Magnet

Comprehensive Studies of Magnetic Transitions and Spin–Phonon Couplings in the Tetrahedral Cobalt Complex Co(AsPh₃)₂I₂

Advanced Spectroscopic and Computational Studies of a Cobalt(II) Coordination Polymer with Single-Ion-Magnet Properties

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Molecular Magnets

Cited by 9 publications

References 275 publications

Inter-Kramers Transitions and Spin–Phonon Couplings in a Lanthanide-Based Single-Molecule Magnet

Inter-Kramers Transitions and Spin–Phonon Couplings in a Lanthanide-Based Single-Molecule Magnet

Comprehensive Studies of Magnetic Transitions and Spin–Phonon Couplings in the Tetrahedral Cobalt Complex Co(AsPh3)2I2

Advanced Spectroscopic and Computational Studies of a Cobalt(II) Coordination Polymer with Single-Ion-Magnet Properties

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Comprehensive Studies of Magnetic Transitions and Spin–Phonon Couplings in the Tetrahedral Cobalt Complex Co(AsPh₃)₂I₂