Abstract
Abstract
We report 31P NMR studies of an oriented polycrystalline superconductor of Ba0.5Sr0.5Fe2(As1−x
P
x
)2 with x ∼ 0.4 (T
c = 29 K) at T = 14−325 K and B
0 = 1 and 5 T. The 31P Knight shift Kab
at B
0 ⊥ c shows a nearly T-independent uniform spin susceptibility above T
c and a spin singlet decrease below T
c. The 31P 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
c. The a term in 1/T
1 indicates the presence of two-dimensional antiferromagnetic spin fluctuations. The negative θ = −15 K of the Curie-Weiss-type antiferromagnetic spin susceptibility
χ
(
Q
)
∝
1
/
(
T
+
θ
)
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.
Subject
General Physics and Astronomy
Cited by
1 articles.
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