${}^{31}$P NMR studies of an iron-based superconductor Ba${}_{0.5}$Sr${}_{0.5}$Fe${}_2$(As${}_{1-x}$P${}_x$)${}_2$ with $T_{\mathrm{c}}$ = 29 K

Abstract

We report ${}^{31}$P NMR studies of an oriented polycrystalline superconductor of Ba${}_{0.5}$Sr${}_{0.5}$Fe${}_2$(As${}_{1-x}$P${}_x$)${}_2$ with $x\sim$ 0.4 ($T_{\mathrm{c}}$ = 29 K) at $T$ = 14$-$325 K and $B_0$ = 1 and 5 T. The ${}^{31}$P Knight shift $K_{ab}$ at $B_0\perp c$ shows a nearly $T$-independent uniform spin susceptibility above $T_{\mathrm{c}}$ and a spin singlet decrease below $T_{\mathrm{c}}$. The ${}^{31}$P nuclear spin-lattice relaxation rate 1/$T_1$ shows an asymptotic behavior of $a+bT$ ($a$ and $b$ are constants) at $T>$ 100 K and the minimum at 40 K with an upturn toward $T_{\mathrm{c}}$. The $a$ term in 1/$T_1$ indicates the presence of two-dimensional antiferromagnetic spin fluctuations. The negative $\theta$ = $-$15 K of the Curie-Weiss-type antiferromagnetic spin susceptibility $\chi$($Q$) $\propto$ 1/($T$+$\theta$) in the analysis of 1/$T_{1}T$ suggests antiferromagnetic instability in the superconducting state. Discussions are made from the self-consistent renormalization (SCR) theory for the spin fluctuations with interlayer correlation.

8 pages, 6 figures, accepted for publication in Journal of Physics: Conf. Series 2020

References in corpus (5)

• Nematic and meta-nematic transitions in the iron pnictides
• Commensurate Itinerant Antiferromagnetism in BaFe2As2: 75As-NMR Studies on a Self-Flux Grown Single Crystal
• Interplay between magnetism and superconductivity in Fe-pnictides
• Different response of the crystal structure to isoelectronic doping in BaFe2[As(1-x)P(x)]2 and [Ba(1-x)Sr(x)]Fe2As2
• Antiferromagnetism of SrFe2As2 studied by Single-Crystal 75As-NMR

Cited by in corpus (1)

• Staggered spin susceptibility at a two-dimensional antiferromagnetic quantum critical point