Spin Dynamics in the Paramagnetic Regime: NMR and EPR in Two-Dimensional Magnets

Benner, Hartmut; Boucher, Jean‐Philippe

doi:10.1007/978-94-009-1860-3_7

Cited by 51 publications

(38 citation statements)

References 87 publications

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“…5 and 12. This value is rather small and theoretically unexpected for two-dimensional magnets 28 where such low exponents usually appear only near T N due to 3D antiferromagnetic fluctuations.…”

Section: Resultsmentioning

confidence: 76%

“…While INS can detect S͑Q , ͒ in the full range of frequencies and wave vectors Q, NMR measures the average over Q at Ϸ 0 via the nuclear spin-lattice relaxation rate 1 / T 1 , which, in turn, can be related to the correlation length . 21,28,29 In ESR the linewidth ⌬H is determined by four spin-correlation functions, which in independent-mode approximation can be factorized into products of two spin-correlation functions evaluated at the wave vector of magnetic order and Ϸ 0. 28 The influence of the vortex dynamics on the ESR linewidth was approximately derived by detailed calculations as ⌬H ϰ 3 .…”

Section: Theoretical Backgroundmentioning

confidence: 99%

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Vortex dynamics and frustration in two-dimensional triangular chromium lattices

et al. 2009

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The spin dynamics of the two-dimensional ͑2D͒ triangular lattice antiferromagnets HCrO 2 , LiCrO 2 , and NaCrO 2 is investigated by electron spin resonance. In these oxides, on approaching the Néel temperature T N from above, the divergence of the temperature dependent linewidth is well described in terms of a BerezinskiiKosterlitz-Thouless scenario due to magnetic vortex-antivortex pairing. A refined analysis suggests analogies to the melting scenario of a 2D triangular lattice described by Nelson, Halperin, and Young.

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Section: Resultsmentioning

confidence: 76%

Section: Theoretical Backgroundmentioning

confidence: 99%

Vortex dynamics and frustration in two-dimensional triangular chromium lattices

et al. 2009

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“…20) In the case of the 2D Heisenberg AFM, p is evaluated to be about 2.5 from the experimentally obtained ¼ 0:2 and ¼ 0:95, and p is known to be close to experimental values in several Heisenberg 2D compounds. 21) In NiGa 2 S 4 , we expect that the development of the SRO gives the same critical behavior as in such 2D Heisenberg AFMs. Since there is no LRO down to 0.08 K, 5) we assume that T N is approximate zero.…”

Section: Temperature Dependence Of Esr Linewidthmentioning

confidence: 84%

High-Field ESR and Magnetization of the Triangular Lattice Antiferromagnet NiGa₂S₄

et al. 2010

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We report the experimental and analytical results of electron spin resonance (ESR) and magnetization at high magnetic fields of up to about 68 T of the quasi two-dimensional triangular lattice antiferromagnet NiGa 2 S 4 . From the temperature evolution of the ESR absorption linewidth, we find a distinct disturbance of the development of the spin correlation by Z 2 -vortices between 23 and 8.5 K. Below T v ¼ 8:5 K, spin-wave calculations based on a 57 spiral spin order well explain the frequency dependence of the ESR resonance fields and high-field magnetization processes for H k c and H ? c, although the magnetization for H ? c at high fields is different from the calculated one. Furthermore, we explain the field-independent specific heat with a T 2 dependence by the same spin-wave calculation, but the magnitude of specific heat is much less than the observed one. The single ion anisotropy constant (2010) 023701] is a necessary condition for the realization of a Z 2 -vortex-induced topological transition, which would be destroyed by an extremely small D 6 ¼ 0 in a classical nearest-neighbor spin model owing to the large . Accordingly, these results suggest the occurrence of a Z 2 -vortex-induced topological transition at T v and indicate quantum effects beyond the descriptions based on the above classical spin models, for example, those due to quadrupolar correlations.

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“…6) can originate from the diffusive nature of the spin correlation function, which in one dimension is characterized by longtime tails yielding to a divergence of the low-frequency spectral density J(ω). 17 In fact, in the presence of diffusive processes for the spin excitations 1/T 1 can be written in terms of the spectral density for the spin excitations according to the following equation 18 : pling, which hereafter shall be neglected since A 2 ≫ A 2 d . Then just the second term in square bracket can be considered.…”

Section: Resultsmentioning

confidence: 99%

Low-energy spin dynamics in the[YPc2]0

et al. 2011

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1 H nuclear magnetic resonance (NMR) measurements in [YPc2] 0 , an organic compound formed by radicals stacking along chains, are presented. The temperature dependence of the macroscopic susceptibility, of the NMR shift and of the spin-lattice relaxation rate 1/T1 indicate that the unpaired electron spins are not delocalized but rather form a S = 1/2 antiferromagnetic chain. The exchange couplings estimated from those measurements are all in quantitative agreement. The low-energy spin dynamics can be described in terms of diffusive processes and the temperature dependence of the corresponding diffusion constant suggests that a spin-gap around 1 K might be present in this compound.

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Spin Dynamics in the Paramagnetic Regime: NMR and EPR in Two-Dimensional Magnets

Cited by 51 publications

References 87 publications

Vortex dynamics and frustration in two-dimensional triangular chromium lattices

Vortex dynamics and frustration in two-dimensional triangular chromium lattices

High-Field ESR and Magnetization of the Triangular Lattice Antiferromagnet NiGa₂S₄

Low-energy spin dynamics in the[YPc2]0

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Spin Dynamics in the Paramagnetic Regime: NMR and EPR in Two-Dimensional Magnets

Cited by 51 publications

References 87 publications

Vortex dynamics and frustration in two-dimensional triangular chromium lattices

Vortex dynamics and frustration in two-dimensional triangular chromium lattices

High-Field ESR and Magnetization of the Triangular Lattice Antiferromagnet NiGa2S4

Low-energy spin dynamics in the[YPc2]0

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Product

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High-Field ESR and Magnetization of the Triangular Lattice Antiferromagnet NiGa₂S₄