Publishing type：Research paper (scientific journal)   Publisher：{IOP} Publishing  

<jats:title>Abstract</jats:title>
<jats:p>We report <jats:sup>75</jats:sup>As NMR experiments in heavily electron-doped LaFe<jats:italic>Pn</jats:italic>O<jats:sub>0.75</jats:sub>H<jats:sub>0.25</jats:sub> (<jats:italic>Pn</jats:italic>=As<jats:sub>1−<jats:italic>x</jats:italic>
</jats:sub>Sb<jats:sub>
<jats:italic>x</jats:italic>
</jats:sub> and As<jats:sub>1−<jats:italic>x′</jats:italic>
</jats:sub>P<jats:sub>
<jats:italic>x′</jats:italic>
</jats:sub>) compounds with the maximum <jats:inline-formula>
<jats:tex-math><?CDATA ${T}_{c}^{ { \rm{\max } } }(\sim 33.1{\rm{K } })$?></jats:tex-math>
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll">
<mml:mrow>
<mml:msubsup>
<mml:mi>T</mml:mi>
<mml:mi>c</mml:mi>
<mml:mrow>
<mml:mi mathvariant="normal">max</mml:mi>
</mml:mrow>
</mml:msubsup>
<mml:mo stretchy="false">(</mml:mo>
<mml:mo>∼</mml:mo>
<mml:mn>33.1</mml:mn>
<mml:mi mathvariant="normal">K</mml:mi>
<mml:mo stretchy="false">)</mml:mo>
</mml:mrow>
</mml:math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="JPCS_2323_1_012011_ieqn1.gif" xlink:type="simple" />
</jats:inline-formula>, and compare with the previous results in lightly electron-doped LaFe<jats:italic>Pn</jats:italic>(O,F) compounds. The <jats:italic>T<jats:sub>c</jats:sub>
</jats:italic> of this series can be sensitively controlled by the pnictogen height (<jats:italic>h<jats:sub>Pn</jats:sub>
</jats:italic>) through the substitution at <jats:italic>Pn</jats:italic> site, and the electron doping level through the substitution at the O site with H or F. In heavily electron-doped LaFe<jats:italic>Pn</jats:italic>O(La1111) compounds, we found that spin fluctuations at low-energies were moderately suppressed upon cooling in the Sb-substituted high <jats:italic>T<jats:sub>c</jats:sub>
</jats:italic> compounds with high <jats:italic>h<jats:sub>Pn</jats:sub>
</jats:italic> (<jats:italic>x</jats:italic> ≥ 0), although they are completely suppressed in P-substituted non-superconducting compounds (<jats:italic>x</jats:italic>′ ≥ 0.2) with lower <jats:italic>h<jats:sub>Pn</jats:sub>
</jats:italic>. This feature is largely different from that in the lightly doped La1111 compounds with the well-nested Fermi surfaces, where the spin fluctuations are critically enhanced upon cooling. Here, we present the characteristics of spin fluctuations over wide doping region of La1111-based compounds, and discuss the relationship with the superconductivity.</jats:p>

DOI： 10.1088/1742-6596/2323/1/012011

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society ({APS})  

DOI： 10.1103/physrevb.105.144510

researchmap

Publishing type：Research paper (scientific journal)  

DOI： 10.35848/1882-0786/ac4533

researchmap

Publishing type：Research paper (scientific journal)  

DOI： 10.7566/JPSJ.90.124709

researchmap

Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

Abstract

We report NMR experiments on heavily electron-doped Fe-based superconductor in comparison with the results on the parent Fe-based compounds. The typical parent Fe-based compound LaFe(As_1-x′P_x′)O exhibits the re-emergent antiferromagnetic (AFM) order at x′ ~ 0.6 (AFM2) separated from the parent AFM order at x′ =0 (AFM1). Systematic ³¹P-NMR study on [Sr₄Sc₂O₆]Fe₂(As_1−xP_x)₂ (SrSc42622), which has local lattice parameters of iron-pnictogen (FePn) layer similar to the series of LaFe(As_1−x′/P_x′)O, also revealed that the presence of AFM1 order is universal for most of parent Fe-based compounds. In contrast, the static AFM2 order was absent in this series, however, the dynamical low-energy AFM spin fluctuations are enhanced at around x ~ 0.8, indicating that the onset of the static AFM2 is quite sensitive to the local lattice parameters of FePn layer. In order to elucidate the further universality and diversity, we have carried out ⁷⁷Se-NMR measurement on Li_x(NH₃)_yFe_2−δSe₂ (T_c = 44 K) in heavily electron-doped regime. Although the spin fluctuations at low energies does not significantly develops upon cooling, the moderate spin fluctuations were extracted at high temperatures from comparison of the temperature (T) dependences of Knight shift and nuclear relaxation rate (1/T ₁ T). We discuss the universality and diversity of the relationship between the T_c and the characteristics of the spin fluctuations in the Fe-based compounds from a microscopic point of the NMR measurements.

DOI： 10.1088/1742-6596/1975/1/012008

researchmap

Other Link： https://iopscience.iop.org/article/10.1088/1742-6596/1975/1/012008/pdf

Publishing type：Research paper (international conference proceedings)   Publisher：Journal of the Physical Society of Japan  

DOI： 10.7566/jpscp.30.011147

researchmap