Superconductivity and magnetism in K-doped EuFe<sub>2</sub>As<sub>2</sub>

Anupam,; Paulose, P. L.; Jeevan, H. S.; Geibel, C.; Hossain, Zakir

doi:10.1088/0953-8984/21/26/265701

Cited by 39 publications

(42 citation statements)

References 30 publications

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“…Even rare earths (if present as constituents) develop rather hyperfine fields due to long-range order instead of coupling between the nucleus and the local 4f shell despite the fact that 4f electrons are weakly coupled to the conduction band. 10,30,31 It seems that sample inhomogeneity leading subsequently to magnetic clusters and hyperfine field distribution can be ruled out at least for parent compounds, as the latter are highly ordered structures from the crystallographic point of view. Other mechanisms of magnetic ordering like spin glass formation are even less probable for the compounds in question due to the strongly layered structure.…”

Section: Resultsmentioning

confidence: 99%

Shape of spin density wave versus temperature inAFe2As2<

et al. 2011

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Parent compounds AFe 2 As 2 (A = Ca, Ba, Eu) of the 122 family of the iron-based superconductors have been studied by 57 Fe Mössbauer spectroscopy in the temperature range 4.2-∼300 K. Spin density waves (SDW) have been found with some confidence. They are either incommensurate with the lattice period or the ratio of the respective periods is far away from the ratio of small integers. SDW shape is very unconventional (i.e., differs from the sinusoidal shape). Magnetic order starts with lowered temperature as narrow sheets of the significant electron spin density separated by areas with very small spin density. Magnetic sheets are likely to be ordered in the alternate antiferromagnetic fashion as the material as a whole behaves similarly to the collinear antiferromagnet. A further lowering of temperature simply expands sheet thickness leading to the near triangular SDW. Finally, sheets fill the whole available space and the almost rectangular shape of the SDW is reached. The substantial maximum amplitude of SDW appears at the temperature just below the magnetic onset temperature, and this maximum amplitude increases slightly with lowering temperature. The square root from the mean squared hyperfine field behaves versus temperature according to the universality class (1,2) (i.e., with the electronic spin space having dimensionality equal to unity and the real space having dimensionality equal to 2). The more or less pronounced tail above transition temperature due to the development of incoherent SDW is seen.

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Section: Resultsmentioning

confidence: 99%

Shape of spin density wave versus temperature inAFe2As2<

et al. 2011

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“…6 Like the cuprates, upon proper doping, superconductivity emerges while the magnetic order is suppressed. [7][8][9][10][11][12][13] In the underdoped regime of certain iron pnictides, superconductivity may even coexist with SDW, 14,15 which once again highlights the intimate relation between superconductivity and magnetism in such unconventional superconductors.…”

Section: Introductionmentioning

confidence: 99%

High-resolution angle-resolved photoemission spectroscopy study of the electronic structure ofEuFe2As2

et al. 2010

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We report the high-resolution angle-resolved photoemission spectroscopy studies of electronic structure of EuFe 2 As 2 . The paramagnetic state data are found to be consistent with density-functional calculations. In the antiferromagnetic ordering state of Fe, our results show that the band splitting, folding, and hybridization evolve with temperature, which cannot be explained by a simple folding picture. Detailed measurements reveal that a tiny electron Fermi pocket and a tiny hole pocket are formed near ͑ , ͒ in the ͑0,0͒ − ͑ , ͒ direction, which qualitatively agree with the results of quantum oscillations, considering k z variation in Fermi surface. Furthermore, no noticeable change within the energy resolution is observed across the antiferromagnetic transition of Eu 2+ ordering, suggesting weak coupling between Eu sublattice and FeAs sublattice.

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“…The interaction of the Eu moments with superconductivity in pure and doped EuFe 2 As 2 has been extensively studied. [27][28][29][30][31][32][33] Partial substitution of Eu by K leads to superconductivity in Eu 1−x K x Fe 2 As 2 with T c as high as 33 K for x = 0.5. 27,28,33 Re-entrant superconductivity is observed in EuFe 2 As 2 on application of hydrostatic pressure.…”

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“…[27][28][29][30][31][32][33] Partial substitution of Eu by K leads to superconductivity in Eu 1−x K x Fe 2 As 2 with T c as high as 33 K for x = 0.5. 27,28,33 Re-entrant superconductivity is observed in EuFe 2 As 2 on application of hydrostatic pressure. 30 Like substitution of Co for Fe in BaFe 2 As 2 , Co substitution for Fe in EuFe 2 As 2 also leads to superconductivity but the superconductivity in Eu(Fe 1−x Co x ) 2 As 2 is re-entrant, revealing an important role of the Eu magnetic moment.…”

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Antiferromagnetism inEuCu2As2andEuCu1.82Sb2single crystals

Anand

Johnston

2015

Phys. Rev. B

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Single crystals of EuCu2As2 and EuCu2Sb2 were grown from CuAs and CuSb self-flux, respectively. The crystallographic, magnetic, thermal and electronic transport properties of the single crystals were investigated by room-temperature x-ray diffraction, magnetic susceptibility χ versus temperature T , isothermal magnetization M versus magnetic field H, specific heat Cp(T ) and electrical resistivity ρ(T ) measurements. EuCu2As2 crystallizes in the body-centered tetragonal ThCr2Si2-type structure (space group I4/mmm), whereas EuCu2Sb2 crystallizes in the related primitive tetragonal CaBe2Ge2-type structure (space group P 4/nmm). The x-ray and energy-dispersive x-ray spectroscopy data for the EuCu2Sb2 crystals showed the presence of vacancies on the Cu sites, yielding the actual composition EuCu1.82Sb2. The ρ(T ) and Cp(T ) data reveal metallic character for both EuCu2As2 and EuCu1.82Sb2. Antiferromagnetic (AFM) ordering is indicated from the χ(T ), Cp(T ), and ρ(T ) data for both EuCu2As2 (TN = 17.5 K) and EuCu1.82Sb2 (TN = 5.1 K). In EuCu1.82Sb2, the ordered-state χ(T ) and M (H) data suggest either a collinear A-type AFM ordering of Eu +2 spins S = 7/2 or a planar noncollinear AFM structure, with the ordered moments oriented in the tetragonal ab plane in either case. This ordered-moment orientation for the A-type AFM is consistent with calculations with magnetic dipole interactions. The anisotropic χ(T ) and isothermal M (H) data for EuCu2As2, also containing Eu +2 spins S = 7/2, strongly deviate from the predictions of molecular field theory for collinear AFM ordering and the AFM structure appears to be both noncollinear and noncoplanar.

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Superconductivity and magnetism in K-doped EuFe₂As₂

Cited by 39 publications

References 30 publications

Shape of spin density wave versus temperature inAFe2As2<

Shape of spin density wave versus temperature inAFe2As2<

High-resolution angle-resolved photoemission spectroscopy study of the electronic structure ofEuFe2As2

Antiferromagnetism inEuCu2As2andEuCu1.82Sb2single crystals

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Superconductivity and magnetism in K-doped EuFe2As2

Cited by 39 publications

References 30 publications

Shape of spin density wave versus temperature inAFe2As2<

Shape of spin density wave versus temperature inAFe2As2<

High-resolution angle-resolved photoemission spectroscopy study of the electronic structure ofEuFe2As2

Antiferromagnetism inEuCu2As2andEuCu1.82Sb2single crystals

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Superconductivity and magnetism in K-doped EuFe₂As₂