Dynamics in canonical spin glasses observed by muon spin depolarization

Campbell, I.A.; Amato, A.; Gygax, F. N.; Herlach, D.; Schenck, A.; Cywiński, R.; Kilcoyne, S.H.

doi:10.1103/physrevlett.72.1291

Cited by 158 publications

(102 citation statements)

References 11 publications

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“…Upon decreasing the temperature towards T g one observes β < 1. Two limits are usually discussed, corresponding either: i) to a situation where the coupling between the muons and the local spins has a given distribution, but the local spins have a unique relaxation time at each temperature (in this case one obtains β = 1 2 [26]); or ii) to the so-called concentrated limit, where one assumes an (ideally) unique value for the coupling constant, but a distribution of local spins relaxation time (here a limit β = 1 3 is observed [27]). For our systems, the temperature dependence of β for x = 0.06 and x = 0.5 is plotted as a function of the reduced temperature T /T g in Fig.…”

Section: Resultsmentioning

confidence: 99%

Spin-glass ground state inMn1−xCoxSi

et al. 2010

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We report the discovery of a new spin glass ground state in the transition metal monosilicides with the B20 crystallographic structure. Magnetic, transport, neutron and muon investigation of the solid solution Mn1−xCoxSi have revealed a new dome in the phase diagram with evidence of antiferromagnetic interactions. For Mn rich compounds, a sharp decrease of the Curie temperature is observed upon Co doping and neutron elastic scattering shows that helimagnetic order of MnSi persists up to x = 0.05 with a shortening of the helix period. For higher Co (0.05 < x < 0.90) concentrations, the Curie-Weiss temperature changes sign and the system enters a spin glass state upon cooling (Tg = 9 K for xCo = 0.50), due to chemical disorder. In this doping range, a minimum appears in the resistivity, attributed to scattering of conduction electron by localized magnetic moments.

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Section: Resultsmentioning

confidence: 99%

Spin-glass ground state inMn1−xCoxSi

et al. 2010

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“…Here the electronic spins in the CuO 2 planes fluctuate so fast that they do not affect the muon polarization. At low enough temperatures, typical of other spin glass systems, 18,[20][21][22][23][24][25] there is a fast relaxation due to a static distribution of random local fields, followed by a long-time tail with a slower relaxation resulting from remnant dynamical processes within the spin glass. By decoupling experiments in a longitudinal field we also confirmed the static nature of the magnetic ground state and at very low temperatures oscillations in the asymmetry were observed for pр0.08.…”

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“…[21][22][23][24] We have also tested other methods of analyzing the data as well as a different choice of criteria, for example choosing ␤ϭ0.3 instead of 0.5, to identify T g . 24 found to affect slightly the magnitude of T g and T f but not the trends with doping. We note that our values for T g agree with published data obtained from different techniques, where available.…”

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“…Between the high and low temperature limits the spin correlations slow down through the experimental SR time window and modify the depolarization process in a distinctive fashion. [22][23][24][25] To study the doping dependence of this slowing down we determine two characteristic temperatures. ͑i͒ The temperature, T f , where the spin correlations first enter the SR time window, i.e., where the muon asymmetry first deviates from Gaussian behavior and ͑ii͒ the temperature, T g , at which these correlations freeze into a glassy state thus causing an initial rapid decay in the asymmetry.…”

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Evidence for a generic quantum transition in high-Tccuprates

Tallon²,

et al. 2002

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We study the low-energy spin fluctuations and superfluid density of a series of pure and Zn-substituted high-T c superconductors ͑HTS͒ using the muon spin relaxation and ac-susceptibility techniques. At a critical doping state, p c , we find ͑i͒ simultaneous abrupt changes in the magnetic spectrum and in the superconducting ground state and ͑ii͒ that the slowing down of spin fluctuations becomes singular at Tϭ0. These results provide experimental evidence for a quantum transition that separates the superconducting phase diagram of HTS into two distinct ground states. DOI: 10.1103/PhysRevB.66.064501 PACS number͑s͒: 74.72.Ϫh, 74.25.Ha, 75.40.Ϫs, 76.75.ϩi Quantum phase transitions occur at zero temperature at a critical electron density separating distinct ground states. Near a quantum critical point, electrons in metals are highly correlated and the diverging fluctuations may induce unconventional superconductivity. [1][2][3][4][5][6][7][8] For example, in certain heavy fermion compounds a ''bubble'' of superconductivity occurs around the quantum critical point at which itinerant antiferromagnetism is suppressed by applied pressure. 9 The search for an underlying quantum phase transition in high-T c superconductors ͑HTS͒ is motivated by the potential for quantum fluctuations to bind electronic carriers into superconducting Cooper pairs and also to cause the celebrated linear temperature dependence of their electrical resistivity. [1][2][3][4][5][6][7][8]10 HTS exhibit a common generic phase diagram in which the superconducting transition temperature, T c , rises to a maximum at an optimal doping of approximately 0.16 holes per planar copper atom and then falls to zero on the overdoped side. In addition the underdoped normal state exhibits correlations, which introduce a gap in the density of states that strongly affects all physical properties. There is no phase transition associated with the opening of this gap and so it is called a pseudogap. Analysis of specific heat data, for example, suggests that the pseudogap energy decreases with doping and falls to zero at a critical doping of p c Ӎ0.19, just beyond optimal doping, 10,11 a behavior rather analogous to the quantum-critical heavy-fermion materials. 9 Many fundamental physical quantities such as the superconducting condensation energy, 10,11 the superfluid density, 12,13 and the quasiparticle weight, 10,14 show abrupt changes as p→p c . While compelling in their totality, 10,11 none of the results can be considered as evidence of a quantum transition. In particular there is no evidence for an associated order parameter and slowing down of the relevant fluctuations. With this in mind we examined the evolution with doping of the low-energy spin fluctuation spectrum using muon spin relaxation ( SR) combined with low-field ac-susceptibility measurements of the superfluid density.The samples studied were: ͑i͒ La 2Ϫx Sr x Cu 1Ϫy Zn y O 4 ͑LSCO͒ (xϭ0.03-0.24 and yϭ0, 0.01, and 0.02͒. Samples were synthesized using solid-state reaction and where necessary follow...

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“…This particular relaxation function is known as a stretched exponential function, and has proved very successful in the description of the dynamics of spin-glasses in the paramagnetic regime. 42,43 The multiplicative combination for the magnetic and nuclear relaxation functions in Eq. 5 is valid providing that the nuclear and atomic fields contribute independently to the muon depolarization.…”

Section: Muon Spin Relaxation Measurementsmentioning

confidence: 99%

Structural and dynamical study of moment localization inβ-Mn1−xInx

Stewart

Hillier

et al. 2010

Phys. Rev. B

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We have used neutron scattering and muon spin relaxation (µSR) to investigate the structural and magnetic properties of the β-phase of elemental manganese doped with dilute amounts of indium. β-Mn is an example of a topologically frustrated antiferromagnetically correlated metal -but which remains paramagnetic at all temperatures. The addition of In to β-Mn results in a vast volume expansion of the lattice, and would therefore be expected to have a major effect on the stability and localization of the Mn moment -as observed in, for example, Ru and Al doped β-Mn alloys. We find that In doping in β-Mn results in a short-range ordered spin-glass like ground state, similar to that of Al-doped β-Mn but with residual low frequency spin fluctuations. This is in contrast to Ru doping which results in the stabilization of a long-range ordered Mn moment

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Dynamics in canonical spin glasses observed by muon spin depolarization

Cited by 158 publications

References 11 publications

Spin-glass ground state inMn1−xCoxSi

Spin-glass ground state inMn1−xCoxSi

Evidence for a generic quantum transition in high-Tccuprates

Structural and dynamical study of moment localization inβ-Mn1−xInx

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