Critical current density and flux pinning in Zr0.96V0.04B2 superconductor with AlB2 structure

Abstract

We have investigated the critical current density (Jc) and the flux pinning behavior in Zr0.96V0.04B2 superconductor with an AlB2 structure. V substitutions in Zr sites of non-superconducting ZrB2 system lead to superconductivity, and the 4% V-substituted Zr0.96V0.04B2 compounds show the highest superconducting transition temperature (Tc) of ∼8.7 K. The magnetic hysteresis (M−H) loops for the Zr0.96V0.04B2 demonstrate type-II superconducting behavior in a broad temperature range, and the Jc is estimated from the M−H loops using the Bean model. The analysis of the double-logarithmic Jc(H) plots indicates the dominance of collective pinning in Zr0.96V0.04B2, and that Jc(H) and magnetic field dependences of the flux pinning force density (Fp) are well fitted by the double exponential model which takes into account the existence of two superconducting gaps.

Study of the new superconducting compound Zr0.97V0.03B2 with point-contact spectroscopy

“…1 showing the X-ray diffraction data. The crystalline structure is type AlB 2 , with space group P 6/mmm and lattice parameters determined as a = 3.16(5) Å, and c = 3.626 Å, similar to the found by other researchers [24,25].…”

“…In this work we focus on the study of the induced superconductivity in ZrB 2 by replacing Zr by small quantities of Vanadium. The highest transition temperature obtained at date was T C ≈ 9.3 K, obtained with a substitution of 3 to 4% of Vanadium following a procedure similar to the described by [21][22][23][24][25][26]. Our resulting composition was Zr 0.97 V 0.03 B 2 .…”

Doping-induced superconductivity of ZrB$_2$ and HfB$_2$

“…31 In this case, it is claimed that the electrons fill the σ band and holes occupy the π band, therefore making charge compensation impossible. Furthermore, a recent paper 32 supports the hypothesis of two gaps in Zr 0.96 V 0.04 B 2 from critical current density J c measurements in different fields. In fact, J c can suitably be fitted by the sum of two contributions J 1 and J 2 , respectively, related to the first and the second gap, following an exponential trend as a function of the applied magnetic field.…”

Doping-induced superconductivity of ZrB2 and HfB2

“…In this case, it is claimed that the electrons fill the σ band and holes occupy the π band, therefore making charge compensation impossible. Furthermore, a recent paper [32] supported the hypothesis of two gaps in Zr 0.96 V 0.04 B 2 from critical current density J c measurements in different fields. In fact, J c can suitably be fitted by the sum of two contributions J 1 and J 2 , respectively, related to the first and the second gap, following an exponential trend as a function of the applied magnetic field.…”