TY - JOUR

T1 - Multiple transition temperature enhancement in superconducting TiNbMoTaW high entropy alloy films through tailored N incorporation

AU - Pristáš, Gabriel

AU - Gruber, Georg

AU - Orendáč, Matúš

AU - Bačkai, Július

AU - Kačmarčík, Jozef

AU - Košuth, Filip

AU - Gabáni, Slavomír

AU - Szabó, Pavol

AU - Mitterer, Christian

AU - Flachbart, Karol

N1 - Publisher Copyright: © 2023

PY - 2023/10/12

Y1 - 2023/10/12

N2 - We report about the influence of nitrogen incorporation on the superconducting transition temperature T C of TiNbMoTaW high entropy alloy films deposited using high power impulse magnetron sputtering. By measuring the temperature dependence of resistivity of (TiNbMoTaW)N x nitrides, we observe a significant increase of T C, from 0.62 K for x = 0 up to 5.02 K for x = 0.74. With further increase of x, T C is decreasing and reaches 1.08 K for x = 0.97. The eightfold T C enhancement seems to be associated with the incorporation of light N atoms into the face-centered cubic lattice and with the x dependent enhancement of the electron-phonon interaction, which may be related to the high configuration entropy in high entropy alloys. Measurements in magnetic field show that the upper critical fields B c2 of (TiNbMoTaW)N x with x > 0.15 provide B c2/T C > 2 T/K ratios, which are above the weak-coupling pair breaking limit. Additional heat capacity and point contact spectroscopy measurements show that the superconductivity in the ∼1 μm thick films is bulk in nature, consistent with conventional weak-coupling phonon mediated superconductivity. The proposed strategy of nitrogen incorporation into high entropy alloys may pave a pathway towards tailoring their superconducting properties, especially their T C.

AB - We report about the influence of nitrogen incorporation on the superconducting transition temperature T C of TiNbMoTaW high entropy alloy films deposited using high power impulse magnetron sputtering. By measuring the temperature dependence of resistivity of (TiNbMoTaW)N x nitrides, we observe a significant increase of T C, from 0.62 K for x = 0 up to 5.02 K for x = 0.74. With further increase of x, T C is decreasing and reaches 1.08 K for x = 0.97. The eightfold T C enhancement seems to be associated with the incorporation of light N atoms into the face-centered cubic lattice and with the x dependent enhancement of the electron-phonon interaction, which may be related to the high configuration entropy in high entropy alloys. Measurements in magnetic field show that the upper critical fields B c2 of (TiNbMoTaW)N x with x > 0.15 provide B c2/T C > 2 T/K ratios, which are above the weak-coupling pair breaking limit. Additional heat capacity and point contact spectroscopy measurements show that the superconductivity in the ∼1 μm thick films is bulk in nature, consistent with conventional weak-coupling phonon mediated superconductivity. The proposed strategy of nitrogen incorporation into high entropy alloys may pave a pathway towards tailoring their superconducting properties, especially their T C.

UR - http://www.scopus.com/inward/record.url?scp=85174142484&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2023.119428

DO - 10.1016/j.actamat.2023.119428

M3 - Article

VL - 262.2024

JO - Acta materialia

JF - Acta materialia

SN - 1359-6454

IS - 1 January

M1 - 119428

ER -