Successive transition from superconducting to antiferromagnetic phase in (Ca6(Al, Ti)4Oy)Fe2As2 studied via 75As and 27Al NMR

T. Nakano; N. Fujiwara; S. Tsutsumi; H. Ogino; K. Kishio; J. Shimoyama

doi:10.1103/PhysRevB.84.060502

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Successive transition from superconducting to antiferromagnetic phase in (Ca6(Al, Ti)4Oy)Fe2As2 studied via 75As and 27Al NMR

T. Nakano, N. Fujiwara, S. Tsutsumi, H. Ogino, K. Kishio, J. Shimoyama

DOI 10.1103/PhysRevB.84.060502 · Physical Review B

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Abstract

An unusual successive phase transition from superconducting (SC) to antiferromagnetic (AF) phases was discovered via 75As and 27Al nuclear magnetic resonance (NMR) in (Fe2As2)(Ca6(Al, Ti)4Oy) with four (Al, Ti)O layers intercalated between FeAs planes. Although the spatially uniform AF ordering is clearly visible from 27Al spectra, the ordered moments are very small and the low-frequency fluctuation is much suppressed, contrary to existing pnictides with localized magnetic elements. Furthermore, the temperature (T) dependence of the fluctuation at both nuclei is very similar throughout the entire temperature range. These facts suggest that some hybridization between Ti and Fe orbitals induces a uniform electronic state within FeAs and (Al, Ti)O layers accompanied by the SC and AF transitions. The iron-based pnictide with Ti-doped blocking layers is the first high-Tc compound having metallic blocking layers.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
(Fe2As2)(Ca6(Al,Ti)4Oy) Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	39	Pressure not reported	onset
(Fe2As2)(Ca6(Al,Ti)4Oy) Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	30	Pressure not reported	zero_resistance
(Fe2As2)(Ca6(Al,Ti)4Oy) Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	36.8	Pressure not reported	unknown
LaFeAsO1-xFx Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
Ba(Fe1-xCox)2As2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
CaFe1-xCoxAsF Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown
(Fe2As2)(Ca4(Mg,Ti)3Oy) Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	47	Pressure not reported	unknown
(Fe2As2)(Ca5(Sc,Ti)4Oy) Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	40	Pressure not reported	unknown
(Fe2As2)(Ca6(Sc,Ti)5Oy) Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	40	Pressure not reported	unknown
(Fe2As2)(Sr4(Mg,Ti)2O6) Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	35	Pressure not reported	unknown
(Fe2As2)(Sr4V2O6) Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	37	Pressure not reported	unknown