Superconductivity and phase diagrams of CaK(Fe_1-xMn_x)₄As₄ single crystals

Journal Article · Tue Jun 28 00:00:00 EDT 2022 · Physical Review. B

DOI:https://doi.org/10.1103/physrevb.105.214526· OSTI ID:1874801

Xu, M. ^[1]; Schmidt, J. ^[1]; Gati, E. ^[2]; Xiang, L. ^[1]; Meier, W. R. ^[3]; Kogan, V. G. ^[1]; Bud'ko, S. L. ^[1]; Canfield, P. C. ^[1]

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1. Ames Lab., and Iowa State University, Ames, IA (United States)
2. Ames Lab., and Iowa State University, Ames, IA (United States); Max Planck Institute for Chemical Physics of Solids, Dresden (Germany)
3. Ames Lab., and Iowa State University, Ames, IA (United States); University of Tennessee, Knoxville, TN (United States)

In order to study the effects of Mn substitution on the superconducting and magnetic ground state of CaKFe₄As₄ (T_c = 35 K), members of the CaK (Fe_1–xMn_x)₄As₄ series have been synthesized by high-temperature solution growth in single-crystalline form and characterized by elemental analysis, thermodynamic, and transport measurements. 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 0.036. For x values greater than 0.016, signatures of a magnetic transition can be detected in both thermodynamic and transport measurements in which kinklike features allow for the determination of the transition temperature T* that increases as Mn substitution increases. Here, a temperature-composition (T–x) phase diagram is constructed, revealing a half-dome of superconductivity with the magnetic transition temperature T* appearing near 26 K for x ~ 0.017 and rising slowly up to 33 K for x ~ 0.036. In addition to the creation of the T–x phase diagram for CaK(Fe_1–xMn_x)₄As₄, specific-heat data are used to track the jump in specific heat at T_c; the CaK(Fe_1–xMn_x)₄As₄ data do not follow the scaling of ΔC_p with $$T$$$^{3}_{c}$$ as many of the other Fe-based superconducting systems do. These data suggest that, as magnetic pair breaking is present, the jump in C_p for a given T_c is reduced. Elastoresistivity coefficients 2m₆₆ and m₁₁ – m₁₂ as a function of temperature are also measured. 2m₆₆ and m₁₁ – m₁₂ are qualitatively similar to CaK(Fe_1–xNi_x)₄As₄. This may indicate that the magnetic order in Mn-substituted system may be still the same as CaK(Fe_1–x Mn_x)₄As₄ . Superconductivity of CaK(Fe_1–x Mn_x)₄As₄ 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 ~ 0.015 is observed and probably is related to change of the Fermi surface due to magnetic order. Coherence lengths and the London penetration depths are also calculated based on H_c1 and H_c2 data. Coherence lengths as the function of x also show the changes near x = 0.015, 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: Gordon and Betty Moore Foundations; USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division; W. M. Keck Foundation
• Grant/Contract Number: AC02-07CH11358
• OSTI ID: 1874801
• Report Number(s): IS-J-10,844; GBMF4411
• Journal Information: Physical Review. B, Journal Name: Physical Review. B Journal Issue: 21 Vol. 105; ISSN 2469-9950
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
crystal growth
iron-based superconductors
magnetization measurements
resistivity measurements
superconductivity
superconductors