Magnetic spin-lattice relaxation in nuclear quadrupole resonance: the eta not=0 case

Chepin, James; Ross, Joseph H.

doi:10.1088/0953-8984/3/41/009

Cited by 69 publications

(51 citation statements)

References 18 publications

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“…59 Co NQR measurements were carried out by using a phase-coherent spectrometer. The nuclear magnetization decay curve is excellently fitted to the theoretical curves [24], with a unique T 1 component. Figure 1(a) shows a typical example of the three NQR transition lines arising from the nuclear spin I=7/2 of 59 Co. Figure 1(b) shows the ± 3/2↔±5/2 transition line for various Na contents.…”

Section: Resultsmentioning

confidence: 78%

Na content dependence of superconductivity and the spin correlations in Na_xCoO₂·1.3H₂O

鄭

Matano

Meng

et al. 2006

J. Phys.: Condens. Matter

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Abstract.We report systematic measurements using 59 Co nuclear quadrupole resonance (NQR) technique on the cobalt oxide superconductors Na x CoO 2 ·1.3H 2 O over a wide Na content range x=0.25∼ 0.34. We find that T c increases with decreasing x but reaches to a plateau for x ≤0.28. In the sample with x ∼0.26, the spin-lattice relaxation rate 1/T 1 shows a T 3 variation below T c and down to T ∼ T c /6, which unambiguously indicates the presence of line nodes in the superconducting (SC) gap function. However, for larger or smaller x, 1/T 1 deviates from the T 3 variation below T ∼ 2 K even though the T c (∼4.7 K) is similar, which suggests an unusual evolution of the SC state. In the normal state, the spin correlations at a finite wave vector become stronger upon decreasing x, and the density of states at the Fermi level increases with decreasing x, which can be understood in terms of a single-orbital picture suggested on the basis of LDA calculation.

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Section: Resultsmentioning

confidence: 78%

Na content dependence of superconductivity and the spin correlations in Na_xCoO₂·1.3H₂O

鄭

Matano

Meng

et al. 2006

J. Phys.: Condens. Matter

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“…In the case of finite η, the recovery function was calculated by numerical diagonalization of the master equation for nuclear relaxation. [28] For the Sn substitutions, 1/T 1 is reduced on average, and the variation in the magnitude of 1/T 1 is small. 1/T 1 values for the bulk A and satellite D peaks show a maximum, while those for B and C peaks are diminished.…”

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confidence: 92%

Microscopic investigation of electronic inhomogeneity induced by substitutions in a quantum critical metalCeCoIn5

et al. 2015

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“…The RðtÞ data measured at the PM 8.3 MHz signal at 4.2 K can be fit consistently by the theoretical function for I ¼ 7=2 with a single T 1 component. 16,17) Below 2.3 K, 1=T 1 was measured at the FM 8.1 MHz 59 Co-NQR peak and is still described by a single component down to T SC . Below T SC , slower relaxation component was observed in RðtÞ and this tendency is more pronounced as temperature is lowered.…”

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confidence: 97%

Microscopic Coexistence of Ferromagnetism and Superconductivity in Single-Crystal UCoGe

et al. 2010

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Unambiguous evidence for the microscopic coexistence of ferromagnetism and superconductivity in UCoGe (T Curie $ 2:5 K and T SC $ 0:6 K) is reported from 59 Co nuclear quadrupole resonance (NQR). The 59 Co-NQR signal below 1 K indicates ferromagnetism throughout the sample volume, while the nuclear spin-lattice relaxation rate 1=T 1 in the ferromagnetic (FM) phase decreases below T SC due to the opening of the superconducting (SC) gap. The SC state is found to be inhomogeneous, suggestive of a self-induced vortex state, potentially realizable in a FM superconductor. In addition, the 59 Co-NQR spectrum around T Curie shows that the FM transition in UCoGe possesses a first-order character, which is consistent with the theoretical prediction that the low-temperature FM transition in itinerant magnets is generically of first-order.KEYWORDS: ferromagnetic superconductor, U-based heavy-fermion, UCoGe, nuclear quadrupole resonance DOI: 10.1143/JPSJ.79.023707After the discovery of superconductivity in UGe 2 under pressure, 1) the coexistence of superconductivity and ferromagnetism becomes one of the major topics in condensedmatter physics. This is because ferromagnetism and spinsinglet superconductivity are thought to be mutually exclusive. 2,3) In the presence of a large splitting between the majority and minority spin Fermi surfaces, as in a ferromagnetic (FM) state, more-exotic spin-triplet superconductivity is allowed, in which parallel spins pair within each spin Fermi surface. While FM superconductors such as UIr 4) and URhGe 5) have recently been demonstrated to occur experimentally, proof that the same charge carriers participate simultaneously in both phenomena has remained elusive.In 2007, new ambient-pressure ferromagnetic (FM) superconductor UCoGe was discovered by Huy et al.6) UCoGe is a weak ferromagnet with T Curie ¼ 3 K and the ordered moments s ¼ 0:03 B , and shows superconductivity at the transition temperature T SC ¼ 0:8 K, 6) highest among FM superconductors. In order to investigate the correlation between ferromagnetism and superconductivity, nuclear quadrupole resonance (NQR) measurements are ideally suited, since they provide microscopic information about the electronic and magnetic properties without applying external fields. In a magnetically ordered state, the NQR signal splits or shifts due to internal fields at the nuclear site, and the nuclear spin-lattice relaxation rate 1=T 1 provides siteselective information about the density of states at the Fermi level and thus about the superconducting (SC) gap structure. UCoGe is a FM superconductor suitable for NQR measurements, since it contains an NQR-active element of 59 Co. In the previous letter, we reported 59 Co-NQR studies in a polycrystalline UCoGe with T Curie ¼ 2:5 K and the SC onset temperature T onset SC ¼ 0:7 K. 7) We found inhomogeneous ferromagnetism below T Curie in the polycrystalline sample, from the observation of the FM and paramagnetic (PM) NQR spectra at lowest temperature. In addition, the SC anomaly was observed in 1=T 1 mea...

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Magnetic spin-lattice relaxation in nuclear quadrupole resonance: the eta not=0 case

Cited by 69 publications

References 18 publications

Na content dependence of superconductivity and the spin correlations in Na_xCoO₂·1.3H₂O

Na content dependence of superconductivity and the spin correlations in Na_xCoO₂·1.3H₂O

Microscopic investigation of electronic inhomogeneity induced by substitutions in a quantum critical metalCeCoIn5

Microscopic Coexistence of Ferromagnetism and Superconductivity in Single-Crystal UCoGe

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Magnetic spin-lattice relaxation in nuclear quadrupole resonance: the eta not=0 case

Cited by 69 publications

References 18 publications

Na content dependence of superconductivity and the spin correlations in NaxCoO2·1.3H2O

Na content dependence of superconductivity and the spin correlations in NaxCoO2·1.3H2O

Microscopic investigation of electronic inhomogeneity induced by substitutions in a quantum critical metalCeCoIn5

Microscopic Coexistence of Ferromagnetism and Superconductivity in Single-Crystal UCoGe

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Na content dependence of superconductivity and the spin correlations in Na_xCoO₂·1.3H₂O

Na content dependence of superconductivity and the spin correlations in Na_xCoO₂·1.3H₂O