scispace - formally typeset
Search or ask a question
Topic

Relaxation (NMR)

About: Relaxation (NMR) is a research topic. Over the lifetime, 29342 publications have been published within this topic receiving 689851 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: In this article, high-field EPR studies of high-spin trigonal bipyramidal Ni(II) complexes have been conducted to confirm an unprecedented axial magnetic anisotropy, which pushes the limits of the familiar spin-only description.
Abstract: Monometallic complexes based on 3d transition metal ions in certain axial coordination environments can exhibit appreciably enhanced magnetic anisotropy, important for memory applications, due to stabilisation of an unquenched orbital moment. For high-spin trigonal bipyramidal Ni(II), if competing structural distortions can be minimised, this may result in an axial anisotropy that is at least an order of magnitude stronger than found for orbitally non-degenerate octahedral complexes. Broadband, high-field EPR studies of [Ni(MDABCO)2Cl3]ClO4 (1) confirm an unprecedented axial magnetic anisotropy, which pushes the limits of the familiar spin-only description. Crucially, compared to complexes with multidentate ligands that encapsulate the metal ion, we see only a very small degree of axial symmetry breaking. 1 displays field-induced slow magnetic relaxation, which is rare for monometallic Ni(II) complexes due to efficient spin–lattice and quantum tunnelling relaxation pathways.

118 citations

Journal ArticleDOI
TL;DR: In this article, the electron spin relaxation processes for oblate and prolate symmetric top paramagnetic probes dissolved in liquid crystals are studied by solving the diffusion equation for molecules subjected to an orienting potential, expressed as a series expansion of Legendre polynomials.
Abstract: The electron spin relaxation processes for oblate and prolate symmetric top paramagnetic probes dissolved in liquid crystals are studied by solving the diffusion equation for molecules subjected to an orienting potential, expressed as a series expansion of Legendre polynomials. The line shape variations upon ordering have been calculated for vanadyl complexes and nitroxide radicals, and the effect of the contributions of quadratic and quartic terms of the potential energy function, and of the diffusion tensor anisotropy have been examined.

118 citations

Journal ArticleDOI
TL;DR: It was found that the intermolecular interactions have a significant effect on the manifestation of slow relaxation of the magnetization, and thereby, these complexes represent a new family of "exchange-biased single-molecule magnets", where the exchange bias is controlled by chemical and structural modifications.
Abstract: A new family of tetranuclear Mn complexes [Mn4X4L4] (H2L = salicylidene-2-ethanolamine; X = Cl (1) or Br (2)) and [Mn4Cl4(L‘)4] (H2L‘ = 4-tert-butyl-salicylidene-2-ethanolamine, (3)) has been synthesized and studied. Complexes 1−3 possess a square-shaped core with ferromagnetic exchange interactions between the four MnIII centers resulting in an S = 8 spin ground state. Magnetochemical studies and high-frequency EPR spectroscopy reveal an axial magnetoanisotropy with D values in the range −0.10 to −0.20 cm-1 for complexes 2 and 3 and for differently solvated forms of 1. As a result, these species possess an anisotropy-induced energy barrier to magnetization reversal and display slow relaxation of the magnetization, which is observed as hysteresis for 1 and 3 and frequency-dependent peaks in out-of-phase AC susceptibility measurements for 3. The effective energy barrier was determined to be 7.7 and 7.9 K for 1 and 3, respectively, and evidence for quantum tunneling of the magnetization was observed. Detail...

118 citations

Journal ArticleDOI
TL;DR: The mechanism of decoherence in solid-state spin qubits subject to low magnetic fields is more complex than previously expected as an additional fast relaxation stage has now been identified as discussed by the authors.
Abstract: The mechanisms of decoherence in solid-state spin qubits subject to low magnetic fields turn out to be more complex than previously expected as an additional fast relaxation stage has now been identified. The control of solid-state qubits requires a detailed understanding of the decoherence mechanisms. Despite considerable progress in uncovering the qubit dynamics in strong magnetic fields1,2,3,4, decoherence at very low magnetic fields remains puzzling, and the role of quadrupole coupling of nuclear spins is poorly understood. For spin qubits in semiconductor quantum dots, phenomenological models of decoherence include two basic types of spin relaxation5,6,7: fast dephasing due to static but randomly distributed hyperfine fields (∼2 ns)8,9,10,11 and a much slower process (>1 μs) of irreversible monotonic relaxation due either to nuclear spin co-flips or other complex many-body interaction effects12. Here we show that this is an oversimplification; the spin qubit relaxation is determined by three rather than two distinct stages. The additional stage corresponds to the effect of coherent precession processes that occur in the nuclear spin bath itself, leading to a relatively fast but incomplete non-monotonic relaxation at intermediate timescales (∼750 ns).

118 citations

Journal ArticleDOI
TL;DR: In this article, the authors used hyperquenching−annealing−calorimetric approach to study the secondary relaxation in La55Al25Ni20 metallic glasses and found that the observed β relaxation exhibits a typical feature of the genuine JG relaxation, i.e., the variation of its activation energy (Eβ) with the glass transition temperature obeys the relation Eβ = 26.8RTg.
Abstract: We report experimental evidence for the existence of Johari−Goldstein (JG) relaxation in metallic glass formers. By using the hyperquenching−annealing−calorimetric approach, we study the dynamics of the secondary (β) relaxation in La55Al25Ni20 metallic glasses. The observed β relaxation exhibits a typical feature of the genuine JG relaxation, i.e., the variation of its activation energy (Eβ) with the glass transition temperature (Tg) obeys the relation Eβ = 26.8RTg. The correlative degree between the β and the primary α relaxations is closely associated with the liquid fragility. By a survey of the sub-Tg relaxation data of other metallic glass systems, we have determined the Eβ values that find the correlation Eβ = 26.1RTg, indicating that JG relaxations are intrinsic in metallic glass formers. By analyzing the primitive relaxation time of the JG motion, τ0,JG, and the crossover time in the Coupling model, tc, we discuss why the excess wing rather than the JG peak (or shoulder) is present in metallic gla...

118 citations


Network Information
Related Topics (5)
Amorphous solid
117K papers, 2.2M citations
88% related
Excited state
102.2K papers, 2.2M citations
87% related
Electron
111.1K papers, 2.1M citations
86% related
Band gap
86.8K papers, 2.2M citations
86% related
Raman spectroscopy
122.6K papers, 2.8M citations
86% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202227
2021652
2020582
2019614
2018638
2017645