Evidence of multiband behavior in the superconducting alloy Zr0.96V0.04B2

Abstract

Evidence of multiband behavior in the superconducting alloy Zr 0.96V0.04B2 ZrB 2 is a nonsuperconducting Pauli paramagnetic crystallizing in the AlB 2 structure. V substitution for Zr in Zr 1−x V x B 2 (0.01 x 0.1) at the few percentage level induces superconductivity with critical temperature reaching a maximum of 8.7 K for Zr 0.96 V 0.04 B 2 near the solid solubility limit. Specific-heat and lower critical field temperature dependence results suggest the possibility of unconventional superconductivity possibly arising from multiband effects.

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

“…1,27 The low J c (0) of the Zr 0.96 V 0.04 B 2 is considered to be due to the poor electrically connectivity between the grains. 28 Furthermore, the irreversible regions lie at much lower fields than the upper critical fields, H c2 (T), determined from the electrical transport measurement, 23 which is usually observed in high-T c superconductors or in superconducting samples with weak pinning. [29][30][31] The double-logarithmic plots for the J c (H) shown in the inset of Fig.…”

“…The details of the fabrication and the basic properties for the Zr 1Àx V x B 2 compounds are described in Ref. 23. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for the structural analysis for the Zr 0.96 V 0.04 B 2 samples after polishing to make a flat surface.…”

“…The XRD data present no diffraction peaks ascribable to impurities, and it is obtained that the lattice constants a-axis and c-axis are a ¼ 3.164 Å and c ¼ 3.524 Å , respectively. The a-axis lattice constant of the Zr 0.96 V 0.04 B 2 is rarely changed compared to ZrB 2 , while the c-axis lattice constant is reduced by $1.7%, 23 which affects the electronic properties and eventually induce superconductivity. The SEM image of the polished Zr 0.96 V 0.04 B 2 sample, shown in the inset in Fig.…”

“…22 Very recently, we have studied the effect of the V substitution for the Zr site in ZrB 2 compounds and found its favorable effect on T c . Interestingly, a small percent of V substitution on the Zr sites induces superconductivity in a non-superconducting ZrB 2 , and 4% V-substituted Zr 0.96 V 0.04 B 2 compounds show a maximum T c of $8.7 K. 23 Moreover, basic properties of these compounds suggest a multiband behavior, and they have a high upper critical field (H c2 (0)) of $16 T in spite of a low T c , which make these material more interesting for further studies. The critical current density (J c ) is one of the important parameters of superconductor, but the research concerning J c of the ZrB 2 with Zr substituted by V has not yet been carried out.…”

Investigação de supercondutividade em boreto do sistema Ta-Zr-B

“…A descoberta da supercondutividade no composto MgB2 (NAGAMATSU et al, 2001;SAMUELY et al, 2005), com temperatura crítica de aproximadamente 40K com a primeira observação de efeito multibanda, reacendeu o interesse em estudar as propriedades dos compostos intermetálicos à base de boro. Recentemente, em um artigo publicado no Physical Review B (RENOSTO et al, 2013) foi mostrado que a substituição de Zr por V no composto de estequiometria Zr1-xVxB2 é capaz de induzir supercondutividade na matriz paramagnética ZrB2 com temperatura crítica de transição supercondutora máxima de 8,7 K. Este resultado, comportamento não usual, também revela forte evidências de comportamento multibanda no composto Zr0.96V0.04B2. No ano de 2015 foi descoberto outro boreto supercondutor que tem composição Ta1-xHfxB com forte manifestação multibanda (MACHADO et al, 2015).…”