Scaling Behavior of the Generalized Susceptibility inLa2−xSrxCu

Abstract

We have measured the static and dynamic spin fluctuations in a crystal of La2-v Sr v Cu04+ > in the spin-glass doping regime. The static spin correlations are well described by a simple model in which the inverse correlation length K(X,T) = S K(X,0) +K(0,T).The dynamic spin fluctuations exhibit a simple scaling behavior in co/T for temperatures 10 K<T<500 K for the measured energies 4.5 <w< 12 meV.PACS numbers: 75.50.Ee, 74.70.Hk, 74.70Jm, 75.40.Cx The nature of the magnetism in the lamellar copper oxides continues to be a subject of extensive study both because of its intrinsic interest and because of its possible role in high-temperature superconductivity. Spin fluctuations in antiferromagnetic, spin-glass, and superconducting samples have been probed using neutron-scattering [1], nuclear-magnetic-resonance [2], and muon-spinresonance techniques [3]. The former two, in particular, have shown the importance of magnetic fluctuations in superconducting samples. Of special importance for the studies reported here is the observation in the La2-x Sr xCuC>4+ v series that the spin fluctuations at low energies (say co -6 meV, using ft=A:# = l as we will throughout) have comparable strengths in antiferromagnetic, spinglass, and superconducting samples [4].In this paper we report on a detailed study of the instantaneous and dynamic spin fluctuations for a crystal of Lai.96Sro.o4Cu04 which is in the intermediate spin-glass regime. These measurements are part of a more global study of the nature of the crossover from antiferromagnetic to spin-glass behavior which will be reported at a later date [5]. However, our results for the dynamics are sufficiently novel and, in our view, important that we wish to report those results separately here. We find that the instantaneous correlations are well described by a simple model in which tc(x,T) -K(X,0) + K(0,T) [5,6]. The spin-spin correlation length, ^ = K: _1 (JC,0), is -40 A and K(X,T) is temperature independent below 300 K. Studies of the dynamics in the CuC>2 plane reveal that the fluctuations are centered about the (K^JT) position (square lattice, unit lattice constant notation) with negligible weight at other high-symmetry positions such as (/r,0) and (2/r,0). Our essential new result is that we find that the integrated response around (K,K) as a function of temperature T exhibits a simple scaling behavior in co/T for temperatures 10 K;S7':<500 K and energies 4.5 meV< co< 12 meV. This scaling leads to a natural explanation of a variety of normal-state properties of the copper oxides.Before discussing the experiments, we note that the transport in our La2-v Sr Y Cu04+ > single crystals has been extensively investigated by Preyer et al. [7]. In the doping regime 0.02 <x ;S0.06, the resistance within the CUO2 planes is metallic and linear in T over a wide range of temperatures above -80 K with an amplitude, normalized to carrier concentration, comparable to that in YBa2Cu307. Below -80 K logarithmic corrections to the resistivity appear, possibly the result of weaklocalizat...

Inelastic neutron scattering study of magnetic excitations inSr2RuO4

“…Since Sr 2 RuO 4 is close to a quantum critical point it is tempting to analyze whether the excitation spectrum is governed by some ω T -scaling, as it has been claimed for the high temperature superconductor La 2−x Sr x CuO 4 [46,47,48] and for CeCu 5.9 Au 0.1 [49]. One would expect that the susceptibility is given by :…”

Two-dimensional incommensurate and three-dimensional commensurate magnetic order and fluctuations in La2−xBaxCuO

“…Most of this work has focussed on La 2−x Sr x CuO 4 , which has been available in large, pristine single crystal form for some time 4 . Although La 2−x Ba x CuO 4 was the original HTS family to be discovered 5 , its study has been greatly restricted due to the difficulty of its single crystal growth.…”

Фрустрированный $J_{1}$-$J_{2}$-$J_{3}$ Квантовый Двумерный Антиферромагнетик В Сферически-Симметричном Самосогласованном Подходе

“…Один из наиболее ярких экспериментальных результатов -это скейлинг χ 2D : за-висимость χ 2D от ω и T хорошо (а при малом допировании -практически идеально) описывается эмпирическим скейлинговым законом [1], [36], [43]- [46] Покажем, что в рамках СССП (15) оказывается возможным аналитически иссле-довать скейлинг восприимчивости χ 2D (ω).…”

“…Там же приведена температур-ная зависимость обратной корреляционной длины ξ −1 . Она хорошо согласуется с экспериментальными данными для La 1.97 Sr 0.03 CuO 4 [43].…”

“…Итак, в рассмотренном аналитическом приближении величина χ 2D (ω) (а следова-тельно, и скейлинговая функцияf (ω/T )) при ω J определяется выражением (23) и представляет собой ступеньку, обращающуюся в нуль при ω ∼ ∆ и размытую на ширину ∼ γ. Однако измерения при гелиевых температурах в слабодопирован-ных купратах демонстрируют отклонение от такого поведения: на самых низких частотах χ 2D (ω) начинает расти и лишь затем обращается в нуль [43]- [45].…”