Magnetic order of the iron spins in NdFeAsO

Chen, Ying; Lynn, J. W.; Li, J.; Li, G.; Chen, G. F.; Luo, Jianlin; Wang, N. L.; Dai, Pengcheng; Cruz, Clarina Dela; Mook, H. A.

doi:10.1103/physrevb.78.064515

Cited by 152 publications

(185 citation statements)

References 33 publications

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“…The spectroscopic measurements also suggest that the R spin ordering does not have any effect on the magnitude of the Fe moment, while for neutron powder diffraction increases have been reported, in particular, for R = Nd. 42,44 In the current case, the available evidence points toward an unchanged Co moment. However, we note that in symmetry unrestricted refinements ͑i.e., by allowing canting out of the basal plane͒ it is possible to obtain solutions with m Co = 0.9͑2͒ B but these are characterized by large correlations and large estimated standard deviations.…”

Section: Discussionmentioning

confidence: 96%

“…20,41 The latter temperature corresponds to the onset of long-range AF order of the Fe spins. 42 For NdFe 1−x Co x AsO ͓x = 0.047͑2͒, x = 0.065͑2͒, and x = 0.123͑2͔͒, data were collected on heating from 4 K. At low temperatures a broadening of reflections with Miller indexes h 0 and k 0, consistent with the well established T → O transition, was evident ͑Fig. 2; supplementary material͒.…”

Section: Structure and Properties Of Ndfe 1−x Comentioning

confidence: 99%

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Superconductivity inNdFe1−xCoxAsO(

et al. 2010

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The phase diagram of NdFe 1−x Co x AsO for low cobalt substitution consists of a superconducting dome ͑0.05Ͻ x Ͻ 0.20͒ with a maximum critical temperature of 16.5͑2͒ K for x = 0.12. The x = 1 end member, NdCoAsO, is an itinerant ferromagnet ͑T C =85 K͒ with an ordered moment of 0.30͑1͒ B at 15 K. Below T N = 9 K, Nd spin ordering results in the antiferromagnetic coupling of the existing ferromagnetic planes. Rietveld analysis reveals that the electronically important twofold tetrahedral angle increases from 111.4°to 115.7°in this series. Underdoped samples with x = 0.046͑2͒ and x = 0.065͑2͒ show distortions to the orthorhombic Cmma structure at 72͑2͒ and 64͑2͒ K, respectively. The temperature dependences of the critical fields H c2 ͑T͒ near T c are linear with almost identical slopes of 2.3͑1͒ T K −1 for x = 0.065͑2͒, x = 0.118͑2͒, and x = 0.172͑2͒. The estimated critical field H c2 ͑0͒ and correlation length for optimally doped samples are 26͑1͒ T and 36͑1͒ Å. A comparison of the maximum reported critical temperatures of well-characterized cobalt-doped 122-and 1111-type superconductors is presented.

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Section: Discussionmentioning

confidence: 96%

Section: Structure and Properties Of Ndfe 1−x Comentioning

confidence: 99%

Superconductivity inNdFe1−xCoxAsO(

et al. 2010

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“…Below the structural distortion the 1:2:2 structure is orthorhombic Fmmm. LiFeAs is tetragonal P4/nmm at all T, Fe (2b, (3/4,1/4,1/2)), As (2c, (1/4,1/4,0.2635)), Li ( [17,18], and PrFeAsO [19,20] [27][28][29] (1:2:2) systems. The crystal structure consists of single Fe-As layers that are separated by a single layer of (for example) LaO or Ba, respectively.…”

Section: Crystal and Magnetic Structuresmentioning

confidence: 99%

Neutron studies of the iron-based family of high TC magnetic superconductors

Lynn

Dai

2009

Physica C: Superconductivity

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We review neutron scattering investigations of the crystal structures, magnetic structures, and spin dynamics of the iron-based RFe(As,P)O (R=La, Ce, Pr, Nd), (Ba,Sr,Ca)Fe 2 As 2 , and Fe 1+x (Te-Se) systems. On cooling from room temperature all the undoped materials exhibit universal behavior, where a tetragonal-to-orthorhombic/monoclinic structural transition occurs, below which the systems become antiferromagnets. For the first two classes of materials the magnetic structure within the a-b plane consists of chains of parallel Fe spins that are coupled antiferromagnetically in the orthogonal direction, with an ordered moment typically less than one Bohr magneton. Hence these are itinerant electron magnets, with a spin structure that is consistent with Fermi-surface nesting and a very energetic spin wave bandwidth ~0.2 eV. With doping, the structural and magnetic transitions are suppressed in favor of superconductivity, with superconducting transition temperatures up to ≈55 K. Magnetic correlations are observed in the superconducting regime, with a magnetic resonance that follows the superconducting order parameter just like the cuprates. The rare-earth moments order antiferromagnetically at low T like 'conventional' magnetic-superconductors, while the Ce crystal field linewidths are affected when superconductivity sets in. The application of pressure in CaFe 2 As 2 transforms the system from a magnetically ordered orthorhombic material to a 'collapsed' non-magnetic tetragonal system. Tetragonal Fe 1+x Te transforms to a low T monoclinic structure at small x that changes to orthorhombic at larger x, which is accompanied by a crossover from commensurate to incommensurate magnetic order.Se doping suppresses the magnetic order, while incommensurate magnetic correlations are observed in the superconducting regime.

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“…1,2,3, 4,5,6,7,8 In the early stages of these investigations, the layered structure of the Fe pnictides superconductors, 1,2,3,4,5,6,7,8 the existence of a magnetic spin striped state revealed by neutron scattering in the undoped limit, 9,10 and their large superconducting critical temperatures 1,2,3,4,5,6,7,8 motivated discussions on a possible close relation between these new Fe-based materials and the high-temperature cuprate superconductors. However, it was clear from the initial investigations that there were substantial differences as well: for example, the resistivity vs. temperature curves of the parent compounds 1,2,3,4,5,6,7,8 do not show the characteristic Mott gapped behavior of, e.g., LaCuO 4 .…”

Section: Introductionmentioning

confidence: 99%

Magnetic and metallic state at intermediate HubbardUcoupling in multiorbital models for undoped iron pnictides

Trinh

Moreo

et al. 2009

Phys. Rev. B

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Multi-orbital Hubbard model Hamiltonians for the undoped parent compounds of the Fe-pnictide superconductors are here investigated using mean-field techniques. For a realistic four-orbital model, our results show the existence of an intermediate Hubbard U coupling regime where the mean-field ground state has spin stripe magnetic order, as in neutron scattering experiments, while remaining metallic, due to the phenomenon of band overlaps. The angle-resolved photoemission intensity and Fermi surface of this magnetic and metallic state are discussed. Other models are also investigated, including a two orbital model where not only the mean-field technique can be used, but also Exact Diagonalization in small clusters and the Variational Cluster Approximation in the bulk. The combined results of the three techniques point toward the existence of an intermediate-coupling magnetic and metallic state in the two-orbital model, similar to the intermediate coupling meanfield state of the four-orbital model. We conclude that the state discussed here is compatible with the experimentally known properties of the undoped Fe-pnictides.

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Magnetic order of the iron spins in NdFeAsO

Cited by 152 publications

References 33 publications

Superconductivity inNdFe1−xCoxAsO(

Superconductivity inNdFe1−xCoxAsO(

Neutron studies of the iron-based family of high TC magnetic superconductors

Magnetic and metallic state at intermediate HubbardUcoupling in multiorbital models for undoped iron pnictides

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