Critical dynamics of a uniaxial and dipolar ferromagnet

Henneberger, S.; Frey, Erwin; Maier, Paul; Schwabl, Franz; Kalvius, Georg Michael

doi:10.1103/physrevb.60.9630

Cited by 14 publications

(12 citation statements)

References 32 publications

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“…It has been suggested that muon-lattice dipolar interactions, known to strongly affect the paramagnetic critical dynamics near a magnetic transition point, could be responsible for the observed low value of the w exponent. 43,44 By considering now the short-time µSR data (see Fig. 11) we can follow the temperature evolution of the internal magnetic field, as sensed at the muon stopping sites.…”

Section: F Muon-spin Relaxationmentioning

confidence: 99%

Magnetic phase diagram of Ca-substituted EuFe2As2

et al. 2018

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The simultaneous presence of a Fe-related spin-density wave and antiferromagnetic order of Eu 2+ moments ranks EuFe 2 As 2 among the most interesting parent compounds of iron-based pnictide superconductors. Here we explore the consequences of the dilution of Eu 2+ magnetic lattice through on-site Ca substitution. By employing macro-and microscopic techniques, including electrical transport and magnetometry, as well as muon-spin spectroscopy, we study the evolution of Eu magnetic order in both the weak and strong dilution regimes, achieved for Ca concentration x(Ca) = 0.12 and 0.43, respectively. We demonstrate the localized character of the Eu antiferromagnetism mediated via RKKY interactions, in contrast with the largely itinerant nature of Fe magnetic interactions. Our results suggest a weak coupling between the Fe and Eu magnetic sublattices and a rapid decrease of the Eu magnetic interaction strength upon Ca substitution. The latter is confirmed both by the depression of the ordering temperature of the Eu 2+ moments, T N , and the decrease of magnetic volume fraction with increasing x(Ca). We establish that, similarly to the EuFe 2 As 2 parent compound, the investigated Ca-doped compounds have a twinned structure and undergo a permanent detwinning upon applying an external magnetic field. arXiv:1805.03896v2 [cond-mat.mtrl-sci]

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Section: F Muon-spin Relaxationmentioning

confidence: 99%

Magnetic phase diagram of Ca-substituted EuFe2As2

et al. 2018

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“…Though, λ is not a strict order parameter, it is a measure of spatial correlation length ξ and can give an idea of critical dynamics: λ ∼ ξ 3/2 for a ferromagnet and λ ∼ ξ 1/2 for an antiferromagnet, whereas ξ ∼ (T /T tr −1) −ν in the close vicinity of the transition temperature T tr [36- [38,40,41]. The fits of λ(T ) are shown by the solid curves in Fig.…”

Section: Muon Spin Relaxation Studymentioning

confidence: 99%

μSRand neutron diffraction investigations on the reentrant ferromagnetic superconductorEu(Fe0.86Ir0.14<

et al. 2015

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Results of muon spin relaxation (µSR) and neutron powder diffraction measurements on a reentrant superconductor Eu(Fe0.86Ir0.14)2As2 are presented. Eu(Fe0.86Ir0.14)2As2 exhibits superconductivity at Tc on ≈ 22.5 K competing with long range ordered Eu +2 moments below ≈ 18 K. A reentrant behavior (manifested by nonzero resistivity in the temperature range 10-17.5 K) results from an exquisite competition between the superconductivity and magnetic order. The zero field µSR data confirm the long range magnetic ordering below TEu = 18.7(2) K. The transition temperature is found to increase with increasing magnetic field in longitudinal field µSR which along with the neutron diffraction results, suggests the transition to be ferromagnetic. The neutron diffraction data reveal a clear presence of magnetic Bragg peaks below TEu which could be indexed with propagation vector k = (0, 0, 0), confirming a long range magnetic ordering in agreement with µSR data. Our analysis of the magnetic structure reveals an ordered magnetic moment of 6.29(5) µB (at 1.8 K) on the Eu atoms and they form a ferromagnetic structure with moments aligned along the c-axis. No change in the magnetic structure is observed in the reentrant or superconducting phases and the magnetic structure remains same for 1.8 K ≤ T ≤ TEu. No clear evidence of structural transition or Fe moment ordering was found.

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“…The third remarkable feature is the thermal behavior of Z which is not unlike the one found for the metallic ferromagnets Fe, Ni, Gd, and GdNi 5 at ambient pressure: [44][45][46] the relaxation rate is found to saturate when approaching T C .…”

Section: Spin-lattice Relaxation Ratementioning

confidence: 99%

Positive muon spin rotation and relaxation measurements on the ferromagnetic superconductorUGe2at ambient and high pressure

et al. 2010

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Results of a detailed investigation of the ferromagnetic superconductor UGe 2 using positive muon spin rotation and relaxation techniques are presented. The pressure and temperature dependences of the frequencies and related spin-spin relaxation rates show that the transition from the weakly to the strongly polarized magnetic ͑WP-SP͒ phases is still observable at T X Ӎ 3 K under a pressure of 1.33͑2͒ GPa. Thus this transition survives at higher pressures than previously believed. The temperature T X at 1.00͑2͒ GPa corresponds to a thermodynamic phase transition rather than a crossover. No such statement can be given reliably at lower pressure. A substantial shrinking of the component along the easy axis of the diagonal hyperfine tensor, at the muon site where it is large, is observed in the SP phase relative to the WP phase. This corresponds to an appreciable decrease in the electronic density at the Fermi level in the SP phase. The investigation of the paramagnetic-ferromagnetic critical spin dynamics at ambient pressure and at 0.95͑2͒ GPa shows that the simple one-band model is an oversimplification inconsistent with our critical spin-dynamics results. Data from specific heat, Fermi-surface studies, Hall effect, neutron form factor, and spectroscopic techniques supports this conclusion. Even at 0.95͑2͒ GPa the conduction electrons are characterized by a small magnetic moment, relative to the bulk magnetization per uranium atom.

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Critical dynamics of a uniaxial and dipolar ferromagnet

Cited by 14 publications

References 32 publications

Magnetic phase diagram of Ca-substituted EuFe2As2

Magnetic phase diagram of Ca-substituted EuFe2As2

μSRand neutron diffraction investigations on the reentrant ferromagnetic superconductorEu(Fe0.86Ir0.14<

Positive muon spin rotation and relaxation measurements on the ferromagnetic superconductorUGe2at ambient and high pressure

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