首页|Magnetic suppression for a possible Fe-poor organic-inorganic hybrid superconductor Fe14Se16(tepa)0.8(tepa=tetraethylenepentamine)with a superconducting transition at～42 K
Magnetic suppression for a possible Fe-poor organic-inorganic hybrid superconductor Fe14Se16(tepa)0.8(tepa=tetraethylenepentamine)with a superconducting transition at～42 K
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Composition/structure-dependent superconductivity for FeSe-based superconductors attracted great at-tention not only due to their high superconducting transition temperatures(Tc),but also for under-standing the origin of iron-based superconductivity.Here,we report a new Fe-poor organic-inorganic hybrid material Fe14Se16(tepa)0.8 with a paramagnetic-diamagnetic transition at～42 K grown by a high-temperature organic-solution-phase method with soluble iron/selenium sources in a tepa solution,alter-native to previous intercalation strategies.The Fe14Se16(tepa)0.8 phase is in a tetragonal layered hybrid structure with a nanoplate shape.Composition analyses reveal a Fe-poor characteristic of the hybrid in contrast to previous FeSe-intercalated superconductor,and selected area electron diffraction pattern is featured by Fe3Se4 superstructures with a √2 × √2 of Fe vacancy order.Ab initio density functional cal-culations show that minus Fe3Se4 ions are stable in the hybrid and～0.25e-/Fe0.7sSe is obviously larger than the reported values of approximately 0.2e-/FeSe in other FeSe-intercalated superconductors.Typ-ical hysteresis loops and temperature dependence of dc/ac susceptibilities of the Fe14Se16(tepa)0.8 mea-sured below～42 K suggest a presence of the Meissner effect in this material.Effects of synthesis condi-tions on structures and magnetic properties of the hybrids show a magnetic evolution from a long-range ferrimagnetic(FIM)order of Fe14Se16(tepa)to a coexistence of FIM and superconducting(SC)orders of Fe14Se16(tepa)0.9 and an SC order of Fe14Se16(tepa)0.8.X-ray absorption spectrum(XAS)confirms the pres-ence of ferric/ferrous irons.Mössbauer studies reveal that the high-Tc superconductivity originates from a suppression of the FIM order through tuning the spin states of irons from high-spin Fe3+(S=5/2)and Fe2+(S=2)in the Fe14Se16(tepa)to low-spin Fe3+(S=1/2)and Fe2+(S=0)in the Fe14Se16(tepa)0.8.Although no zero resistance is detected even at a temperature of 2 K,the resistivity at 2 K decreases by more than 1600 times compared to that in a normal state calculated by a variable range hopping(VRH)model,suggesting that the high-Tc superconductivity of Fe14Se16(tepa)0.8 is possible.
Shenyang National Laboratory for Materials Science,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China
School of Materials Science and Engineering,University of Science and Technology of China,Shenyang 110016,China
Key Lab for Magnetism and Magnetic Materials of the Ministry of Education,Key Lab for Special Functional Materials and Structure Design of the Ministry of Education,Lanzhou University,Lanzhou 730000,China
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