Synthesis and crystal growth of Cs_0.8(FeSe_0.98)₂: a new iron-based superconductor withT_c= 27 K

Abstract

We report on the synthesis of large single crystals of a new FeSe layer superconductor Cs(0.8)(FeSe(0.98))(2). X-ray powder diffraction, neutron powder diffraction and magnetization measurements have been used to compare the crystal structure and the magnetic properties of Cs(0.8)(FeSe(0.98))(2) with those of the recently discovered potassium intercalated system K(x)Fe(2)Se(2). The new compound, Cs(0.8)(FeSe(0.98))(2), shows a slightly lower superconducting transition temperature (T(c) = 27.4 K) in comparison to 29.5 in (K(0.8)(FeSe(0.98))(2)). The volume of the crystal unit cell increases by replacing K by Cs-the c parameter grows from 14.1353(13) to 15.2846(11) Å. For the alkali metal intercalated layered compounds known so far, (K(0.8)Fe(2)Se(2) and Cs(0.8)(FeSe(0.98))(2)), the T(c) dependence on the anion height (distance between Fe layers and Se layers) was found to be analogous to those reported for As-containing Fe superconductors and Fe(Se(1 - x)Ch(x)), where Ch = Te, S.

New Superconducting Phase of Lix(C6H16N2)yFe2−zSe2 with Tc = 41 K Obtained through the Post-Annealing

“…T c 's of the FeSe-based superconductors obtained so far at ambient pressure are summarized in Fig. 6 as a function of d. 1,7,8,10,11,[13][14][15]17,19,20,[23][24][25][26][27] As for the origin of the decrease in T c at d > 9 Å, it may be due to the decrease of the interlayer coupling of cooper pairs. Considering the superconductivity above 100 K in single-layer FeSe films as mentioned above, 6) however, this may be incorrect.…”

Structure and composition of the superconducting phase in alkali iron selenideKyFe1.6+xSe2

“…Of all the iron-based superconductors [1][2][3] , alkali iron selenides A y Fe 1.6+x Se 2 (A = K, Rb, Cs, Tl) [4][5][6][7][8][9] are unique in that superconductivity in this class of materials always coexists with a static long-range antiferromagnetic (AF) order with a large moment and high Néel temperature [10][11][12][13][14] . This is in contrast to iron pnictide superconductors [1][2][3] where optimal superconductivity arises from the suppression of the static AF order in their nonsuperconducting parent compounds 15,16 .…”

Effect of iron content and potassium substitution inA0.8Fe1.6Se2Zhang1, Liu2, He3 et al. 2012Phys. Rev. B174120View full textAdd to dashboardCite

“…28 The purpose of substitution by ions of equal valence but different radii is to alter the chemical pressure to control the electronic properties. An example is the maximum T c of approximately 56 K achieved by the substitution of rare-earth ions in the 1111 system.…”

“…An example is the maximum T c of approximately 56 K achieved by the substitution of rare-earth ions in the 1111 system. 29 It is thus somewhat surprising that substitution of K by Rb, Cs, or Tl in the new superconductors leaves T c essentially unaltered at around 30 K. 28 This result poses another fundamental question, concerning why superconductivity should be so robust in the AFeSe system, and its answer requires a careful investigation into the effect of Tl, Rb, and Cs substitution on the microstructure of the FeSe layers in these materials.…”