Superconductivity and magnetic and transport properties of single-crystalline CaK ( Fe 1 – x Cr x ) 4 As 4

Journal Article · 11 April 2023 · Physical Review. B

DOI: https://doi.org/10.1103/physrevb.107.134511 · OSTI ID:1969556

Xu, Mingyu  ^[1]; Schmidt, J. ^[1]; Tanatar, M. A. ^[1]; Prozorov, R. ^[1]; Bud'ko, S. L. ^[1]; Canfield, P. C. ^[1]

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1. Ames Lab., and Iowa State Univ., Ames, IA (United States)

Members of the CaK (Fe_1–xCr_x)₄ As₄ series have been synthesized by high-temperature solution growth in single-crystalline form and characterized by x-ray diffraction, elemental analysis, and magnetic and transport measurements. The effects of Cr substitution on the superconducting and magnetic ground states of CaKFe₄ As₄ (T_c = 35 K) have been studied. These measurements show that the superconducting transition temperature decreases monotonically and is finally suppressed below 1.8 K as x is increased from 0 to 0.038. For x-values greater than 0.012, signatures of a magnetic transition can be detected in magnetic measurements with the associated features in the transport measurements becoming detectable for x ≥ 0.038. The magnetic transition temperature increases in a roughly linear manner as Cr substitution increases. A temperature-composition (T – x) phase diagram is constructed, revealing a half-dome of superconductivity with the magnetic transition temperature, T*, appearing near 22 K for x ~ 0.017 and rising slowly up to 60 K for x ~ 0.077. The T – x phase diagrams for CaK (Fe_1–xT_x)₄ As₄ for T = Cr and Mn are essentially the same despite the nominally different band filling; this is in marked contrast to T = Co and Ni series for which the T – x diagrams scale by a factor of 2, consistent with the different changes in band filling Co and Ni would produce when replacing Fe. Superconductivity of CaK (Fe_1–xCr_x)₄ As₄ is also studied as a function of magnetic field. A clear change in $$H^{'}_{c2}$$ (T)/T_c, where $$H^{'}_{c2}$$ (T) is dH_c2 (T)/dT, at x ~ 0.012 is observed and probably is related to a change of the Fermi surface due to magnetic order. Further, coherence length and the London penetration depths are also calculated based on H_c1 and H_c2 data. Both of them as a function of x show changes near x = 0.012, again consistent with Fermi surface changes associated with the magnetic ordering seen for higher x-values.

• Research Organization: Ames Laboratory (AMES), Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
• Grant/Contract Number: AC02-07CH11358
• OSTI ID: 1969556
• Report Number(s): IS-J-11,042; {"Journal ID: ISSN 2469-9950",""}
• Journal Information: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 13 Vol. 107; ISSN 2469-9950
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English