Magnetic pair breaking and local lattice distortion in Cr-containing high-entropy alloy superconductors

Nikita Sharma; Tirthankar Chakraborty; Sourav Marik

doi:10.1103/ngx6-vxlq

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Magnetic pair breaking and local lattice distortion in Cr-containing high-entropy alloy superconductors

Nikita Sharma, Tirthankar Chakraborty, Sourav Marik

DOI 10.1103/ngx6-vxlq · Physical Review Materials

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Abstract

High-entropy alloys provide an ideal platform for investigating superconductivity in the presence of extreme chemical disorder, lattice distortion, and magnetic impurity effects. Herein, we report a systematic study of the structural, normal-state, and superconducting-state properties of (TiVTa)0.6Nb0.4−xCrx high-entropy alloys with x=0, 0.05, and 0.20. All compositions crystallize in a single-phase body-centered-cubic structure, with space group Im-3m. Our detailed analysis includes magnetization, resistivity, and specific-heat capacity measurements. The superconducting transition temperature is progressively suppressed from 4.68 to 2.59 K and the upper critical field is decreased from 5.77 to 3.87 T with increasing Cr content in the structure. Heat capacity measurements confirm s-wave weak-coupling superconductivity with a superconducting gap within the BCS limit in all the materials. The suppression of transition temperature follows Abrikosov-Gor'kov behavior, identifying magnetic impurity scattering from Cr as the dominant pair breaking mechanism. First-principles calculation reveals severe local lattice distortion characterized by a large atomic size mismatch δ=5.5% and a substantial average atomic displacement (Δd=0.22Å). The interatomic distance distribution exhibits broadened coordination shells with partially filled gaps between nearest-neighbor shells, reflecting strong deviations from ideal lattice positions while retaining long-range crystalline order.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
(TiVTa)0.6Nb0.4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	4.68	Pressure not reported	onset
(TiVTa)0.6Nb0.35Cr0.05 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	3.9	Pressure not reported	onset
(TiVTa)0.6Nb0.2Cr0.2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.59	Pressure not reported	onset
(TiVTa)0.6Nb0.2Cr0.2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.32	Pressure not reported	onset
(TiVTa)0.6Nb0.4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	4.45	Pressure not reported	onset
Ta34Nb33Hf8Zr14Ti11 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.3	Pressure not reported	unknown
(Ti0.2Zr0.2Nb0.2Hf0.2Ta0.2)C Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.35	Pressure not reported	unknown