One-Dimensional Nuclear Relaxation in Spin 1/2 Systems

Ajiro, Yoshitami; Nakajima, Y.; Furukawa, Yoshihiro; Kiriyama, Hideko

doi:10.1143/jpsj.44.420

Cited by 19 publications

(12 citation statements)

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“…At high temperatures in the uniform AF chain (above T.:), the spin wave correlation length is short, and TIl may be dominated by the one-dimensional diffusive character of the long-wavelength spin excitations (they may not be diffusive 72 ) and is frequency dependent. 73 This frequency dependence becomes less apparent at low temperatures as the diffusive character lessens due to increasing correlation length. At low temperature (but above T.:), TIl also becomes temperature independent as expected for an S = 1/2, one-dimensional AF chain with well-defined excitations.…”

Section: In[t:(p)!t:(o)]mentioning

confidence: 99%

The Spin-Peierls Transition

Bray

Interrante

Jacobs

et al. 1983

Extended Linear Chain Compounds

104

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Section: In[t:(p)!t:(o)]mentioning

confidence: 99%

The Spin-Peierls Transition

Bray

Interrante

Jacobs

et al. 1983

Extended Linear Chain Compounds

104

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“…8,9,10,11,12,13) As to the S = 1/2 chain, an analysis of the ω dependence of 1/T 1 at the Cu site in Sr 2 CuO 3 based on the classical spin-diffusion theory gives an unusually high value of the spin diffusion constant compared with the classical value. 14) This suggests the absence of spin diffusion in the low-temperature limit in consistency with the field-theoretical 2) and perturbative 3) approaches.…”

Section: §1 Introductionmentioning

confidence: 99%

Spin Diffusion in theS=1/2 Quasi One-Dimensional Antiferromagnet α-VO(PO₃)₂via³¹P NMR

et al. 2001

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Low-frequency spin dynamics in the S = 1/2 antiferromagnetic spin-chain compound α-VO(PO3)2 has been studied by means of 31 P NMR. The nuclear spin-lattice relaxation rate 1/T1 at the P site exhibits H −1/2 dependence on the applied magnetic field (H) at temperatures (T ) well above the intrachain coupling strength J/kB = 3.50 K indicating one-dimensional diffusive spin dynamics. The diffusive contribution to 1/T1 decreases on cooling as electronic spins acquire short-range antiferromagnetic correlations within the chain, and vanishes almost entirely around T ≈ J/kB. This is accompanied by an apparent increase of the spin-diffusion constant from the value expected in the classical limit. On the other hand, the field-independent part of 1/T1 increases with decreasing temperature, which may be a precursor for the true long-range antiferromagnetic ordering found below TN = 1.93 ± 0.01 K.KEYWORDS: α-VO(PO 3 ) 2 , NMR, antiferromagnetic spin chain, nuclear spin relaxation, spin diffusion §1. Introduction There has been a continued interest in the dynamics of low-dimensional quantum antiferromagnets at finite temperatures. One of the issues which has attracted renewed attention is a problem of spin diffusion in the one-dimensional (1D) Heisenberg spin chain. It is argued from phenomenology that at high enough temperatures and at long times, the spin autocorrelation function of the 1D Heisenberg spin chain has a diffusive formleading to divergence of the spectral density at low frequencies as ω −1/2 . However, because the diffusive form (1.1) is not derived from the microscopic Hamiltonian but is a consequence of the hydrodynamical assumption for the spin-spin correlation, 1) the question on the existence of spin diffusion in 1D spin chains has been studied intensively from both theoretical and experimental viewpoints. One of the best studied theoretical models is the S = 1/2 XXZ chain represented by the Hamiltonian 2, 3, 4, 5, 6, 7)(1.2)At the isotropic point (∆ = 1) and at low enough temperatures (T ≪ J/k B ), analytical expressions for the dynamical susceptibility χ(q, ω) have been derived for q ≈ 0 and π, and are shown to have no diffusive pole at low frequencies.2) At modestly high, or much higher temperatures compared with the intrachain coupling strength J, the problem is still controversial. Although the absence * E-mail: kikuchi@ph.noda.sut.ac.jp of diffusive excitations seems to be settled for the XXZ chain with planar anisotropy (0 ≤ ∆ < 1), a definite answer for the absence (or presence) of spin diffusion at the isotropic point has not yet been given.Diffusive behavior of the spin-spin correlation has been observed experimentally in several 1D spin chains via the ω −1/2 resonance-frequency dependence of the nuclear spin-lattice relaxation rate 1/T 1 at elevated temperatures. 8,9,10,11,12,13) As to the S = 1/2 chain, an analysis of the ω dependence of 1/T 1 at the Cu site in Sr 2 CuO 3 based on the classical spin-diffusion theory gives an unusually high value of the spin diffusion constant compared with the ...

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“…(5)). This is an unphysical result, which indicates that in Cr 8 and in Cr 7 Cd no spin diffusion can be detected. On the other hand, in Cr 8 Zn it appears that there is a limited range at high fields where spin diffusion could be present.…”

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confidence: 86%

“…10 To date, an experimental investigation of spin dynamics and spin diffusion in Heisenberg magnetic rings and short segments is still lacking. The aim of the present work is twofold: On one hand, we want to study the spin diffusion effects in two nonconventional organic 1D Heisenberg chains: the first, Eu-Et, made up of radical spins and the second, Gd-Et, a frustrated helimagnetic chain; on the other hand, we extend the investigation of spin diffusion to AFM closed molecular rings, such as Cr 8 and broken rings, i.e., segments such as Cr 7 Cd and Cr 8 Zn. It is worth noticing that molecular rings are a class of clusters of transition metal ions covalently bonded via superexchange bridges, embedded in a large organic molecule: 11 such clusters can be synthesized in crystalline form whereby each one is magnetically independent since the intramolecular exchange interaction among the transition metal ions is dominant over the weak intermolecular, usually dipolar, magnetic interaction.…”

Section: Introductionmentioning

confidence: 99%

“…19,20 The aim of the present investigation is to establish if the long time diffusive behavior of the CF observed in 1D Heisenberg chains can also be observed in open rings, which should correspond to 1D finite spin segments. For this purpose, we compare the previous results in closed ring Cr 8 with the results in broken ring Cr 7 Cd, where a magnetic Cr ion is replaced by a diamagnetic Cd ion and in a new kind of ring, Cr 8 Zn, where the eight Cr moments are interrupted by a Zn diamagnetic ion, thus forming a finite spin segment. 21 The experimental results obtained at room temperature for the three rings are plotted in Fig.…”

mentioning

confidence: 99%

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High temperature spin dynamics in linear magnetic chains, molecular rings, and segments by nuclear magnetic resonance

Adelnia

Mariani

Ammannato

et al. 2015

Journal of Applied Physics

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Articles you may be interested inHigh temperature spin dynamics in linear magnetic chains, molecular rings, and segments by nuclear magnetic resonance We present the room temperature proton nuclear magnetic resonance (NMR) nuclear spin-lattice relaxation rate (NSLR) results in two 1D spin chains: the Heisenberg antiferromagnetic (AFM) Eu(hfac) 3 NITEt and the magnetically frustrated Gd(hfac) 3 NITEt. The NSLR as a function of external magnetic field can be interpreted very well in terms of high temperature spin dynamics dominated by a long time persistence of the decay of the two-spin correlation function due to the conservation of the total spin value for isotropic Heisenberg chains. The high temperature spin dynamics are also investigated in Heisenberg AFM molecular rings. In both Cr 8 closed ring and in Cr 7 Cd and Cr 8 Zn open rings, i.e., model systems for a finite spin segment, an enhancement of the low frequency spectral density is found consistent with spin diffusion but the high cut-off frequency due to intermolecular anisotropic interactions prevents a detailed analysis of the spin diffusion regime. V C 2015 AIP Publishing LLC.[http://dx

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One-Dimensional Nuclear Relaxation in Spin 1/2 Systems

Cited by 19 publications

References 18 publications

The Spin-Peierls Transition

The Spin-Peierls Transition

Spin Diffusion in theS=1/2 Quasi One-Dimensional Antiferromagnet α-VO(PO₃)₂via³¹P NMR

High temperature spin dynamics in linear magnetic chains, molecular rings, and segments by nuclear magnetic resonance

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One-Dimensional Nuclear Relaxation in Spin 1/2 Systems

Cited by 19 publications

References 18 publications

The Spin-Peierls Transition

The Spin-Peierls Transition

Spin Diffusion in theS=1/2 Quasi One-Dimensional Antiferromagnet α-VO(PO3)2via31P NMR

High temperature spin dynamics in linear magnetic chains, molecular rings, and segments by nuclear magnetic resonance

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Product

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Spin Diffusion in theS=1/2 Quasi One-Dimensional Antiferromagnet α-VO(PO₃)₂via³¹P NMR