Synthesis, Crystal Structure and Superconductivity in RbLn₂Fe₄As₄O₂(Ln = Sm, Tb, Dy, and Ho)

Abstract

We have synthesized four iron-based oxyarsenide superconductors RbLn 2 Fe 4 As 4 O 2 (Ln = Sm, Tb, Dy and Ho) resulting from the intergrowth of RbFe 2 As 2 and LnFeAsO.It is found that the lattice match between RbFe 2 As 2 and LnFeAsO is crucial for the phase formation. The structural intergrowth leads to double asymmetric Fe 2 As 2 layers that are separated by insulating Ln 2 O 2 slabs. Consequently, the materials are intrinsically doped at a level of 0.25 holes/Fe-atom and, bulk superconductivity emerges at T c = 35.8, 34.7, 34.3 and 33.8 K, respectively, for Ln = Sm, Tb, Dy and Ho. Investigation on the correlation between crystal structure and T c suggests that interlayer couplings may play an additional role for optimization of superconductivity.

Superconductivity at 33–37 K in ALn2Fe4As4O2 (AWu1, Wang2, He3 et al. 2017Phys. Rev. MaterialsSelf Cite382221View full textAdd to dashboardCite

“…We found that T c decreases (increases) with the intra-bilayer (inter-bilayer) spacing. 12,14 In the present K-and Cs-containing series, similar behaviour is expected (here we cannot give the structural correlation plot because some samples' purity is not good enough for a reliable structural refinement).…”

“…Then we also succeeded in synthesizing the first 12442-type oxyarsenide, RbGd 2 Fe 4 As 4 O 2 , whose T c achieves 35 K. 13 With the substitution of rare-earth elements, four additional oxyarsenides in the Rb-containing series have been found. 14 These studies show that the lattice match between 122 and 1111 blocks is important, as suggested in our earlier proposal. 2 For this reason, the lattice-match paradigm can be employed for the exploration of the remaining 12442-type members.…”

“…Similar phenomenon is observed in the RbLn 2 Fe 4 As 4 O 2 series in which the best lattice match is given by Ln = Tb. 14 We thus draw the dashed line in the shaded area of Fig. 1, which marks the best lattice match after the charge-redistribution effect is taken into considerations.…”

BaTh2Fe4As4(N0.7O0.3)2: An iron-based superconductor stabilized by inter-block-layer charge transfer

“…Note that the deviations are the opposite in hole-doped 12442-type FeSCs, the latter of which show larger hAs and smaller  values (e.g., hAs1 = 1.405 Å, hAs2 = 1.436 Å; 1 =108.0  , 2 =106.8  for KCa2Fe4As4F2 16 ). Unlike the (T) behavior in hole-doped 12442-type FeSCs, [16][17][18][19][20] here neither a convex curvature at around 150 K nor a linear temperature dependence below 100 K is seen. The low-temperature (40 K < T < 100 K) normal-state resistivity actually satisfies a power relation,  = 0 + AT n .…”

Growth, properties and magnetism of CaKFe4As4

“…In all four of these examples, the species above and below an Fe-As sheet are the same, preserving the glide-symmetry across the Fe plane. [26,27], AR 2 Fe 4 As 4 O 2 (Ae = Ca, Sr, Ba, Eu; A = K, Rb, Cs; R = lanthanide) [28,29,30] ]. In these families, two different alternating layers separate the Fe-As sheets.…”