Coexistence of incommensurate magnetism and superconductivity inFe1+ySexTe1−x

From antiferromagnetism to superconductivity inFe1+yTe1−xSex

“…Static long-range (LR) magnetic order is suppressed as well on Se doping, although short-range (SR) not commensurate AFM fluctuations are still present in samples with x = 0.25 exhibiting a trace of superconductivity, 6 as well as in superconducting samples with x ranging from 0.30 to 0.416. 5,7 Coexistence between incommensurate SR-AFM and superconductivity has been also reported by Khasanov et al [8] in samples with 0.25 ≤ x ≤ 0.40, whereas commensurate magnetic order prevails for x ≤ 0.10.…”

“…23 In this context it is worth to note that: 1) SR-AFM incommensurate order 5,6,7,8 has been observed in samples with x up to ~0.45, inside which the magnetic volume fractions is strongly dominant (generally exceeding 90%), 8 but characterized by a tetragonal structure at low T; 5,7 2) in both SR and LR-AFM regimes the magnetic wave vector is the same, except for its slight incommensurability in the SR-AFM regime; 3) for pure FeTe the T N obtained by NPD analysis (sensitive only to LR-AFM interactions) and by muon-spin rotation 8 (sensitive also to SR-AFM interactions) is the same, thus suggesting that SR-AFM interactions are absent above the structural transition; 4) the magnetic transition temperatures reported in literature 8 for SR-AFM ordering are in good agreement with those that we obtained for LR-AFM ordering by analysing the neutron thermodiffractograms, as plotted in Figure 13. These facts suggest that LR-AFM order can take place only when the structural transition is not suppressed by Se-substitution in FeTe.…”

Effect of Fe excess on structural, magnetic and superconducting properties of single-crystalline Fe1+xTe1−ySey

“…A systematic investigation of structural, magnetic, and superconducting properties as a function of both the Se-and Fe-content is mandatory, and is the aim of the present work. Single crystals of Fe 1+x Te 1−y Se y have been recently grown by several authors [15,16,20,21,22] and the role of excess Fe in increasing the charge localization has been recognized [16]. However, little attention has been paid to the actual Fe and Se doping levels in a more realistic 3-D phase diagram, and how different ground states can be driven by Fe and Se doping is not yet understood.…”

Interplay of structure, magnetism, and superconductivity in Se substituted iron telluride with excess Fe

“…In others, the two phases coexist in a narrow composition range where the long-range magnetic ordering takes place at temperatures above the superconducting transition [16][17][18]. In iron chalcogenides, on the other hand, an intermediate composition regime exists with short-range magnetic ordering which is characterized by charge carrier localization [19][20][21]. The crossing-over from (π, 0) (defined in the crystallographic Fe 1+y Te lattice) long range order in Fe 1+y Te into a (π, π) magnetic resonance in substituted superconducting Fe 1+y Te 1−x Se x reinforces the view that an intermediate composition regime exists within which short-range magnetic order and superconductivity compete [20,22,23].…”

“…Inelastic neutron scattering studies on superconducting and non-superconducting Fe 1+y Te 1−x Se x also revealed spin fluctuations dominated by incommensurate excitations [25,26]. The suppression of long range magnetic order and the emergence of a superconducting transition with increase in Se composition have been investigated by various groups [11,19,21,27,28]. The temperature composition phase diagram exhibits three regions, as Se composition increased up to 50%: commensurate AFM order followed by a region where incommensurate AFM order and superconductivity coexist, and bulk superconductivity [19].…”