Absence of superconductivity in NbB

Autor(es)

Abud, F. ^[1] ; Correa, L. E. ^[2] ; Souza Filho, I. R. ^[2] ; Machado, A. J. S. ^[2] ; Torikachvili, M. S. ^[3] ; Jardim, R. F. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Fis, Rua Matao 1371, BR-05508090 Sao Paulo, SP - Brazil

^[2] Univ Sao Paulo, Escola Engn Lorena, Caixa Postal 116, BR-12600970 Lorena, SP - Brazil

^[3] San Diego State Univ, Dept Phys, San Diego, CA 92182 - USA

• Tipo de documento: Artigo Científico
• Fonte: PHYSICAL REVIEW MATERIALS; v. 1, n. 4 SEP 8 2017.
• Citações Web of Science: 2

Resumo

A systematic study of the superconducting properties in a series of arc-melted Nb-B samples close to the 1: 1 composition was carried out. Powder x-ray diffraction (XRD) shows that all samples are both nonstoichiometric and composed of two crystal phases: a majority orthorhombic NbB-type phase and traces of a minor body-centered- cubic Nb-rich phase Nb-ss with stoichiometry close to Nb0.98B0.02. The emergence of superconductivity near T-c similar to 9.0 K was inferred from magnetization data in chunk and powder samples. However, the very small superconducting volume fractions are inconsistent with superconductivity arising from the major NbB phase. On the other hand, micrographs of selected samples clearly show that the minority Nb ss forms a three-dimensional network of filaments that meander around the grains of the majority phase, forming a percolation path. Here we report the superconductivity of the Nb ss phase and argue that the low superconducting volume fraction of nonstoichiometric NbB and zero resistance are due to the filaments of the minority phase. The electronic contribution to the entropy of the superconducting state, yielded from an analysis using the a model for single-band systems, indicates that the Sommerfeld constant of the arc-melted samples is close to the values found in nonsuperconducting NbB. Micrograph, XRD, and bulk measurements of magnetization, electrical resistivity, and specific heat suggest that the superconducting state in the NbB samples bearing some Nb ss minority phase is due to the latter. (AU)

• Processo FAPESP: 14/19245-6 - Procura por novos materiais supercondutores
• Beneficiário: Renato de Figueiredo Jardim
• Linha de fomento: Bolsas no Exterior - Pesquisa
• Processo FAPESP: 13/07296-2 - CDMF - Centro de Desenvolvimento de Materiais Funcionais
• Beneficiário: Elson Longo da Silva
• Linha de fomento: Auxílio à Pesquisa - Centros de Pesquisa, Inovação e Difusão - CEPIDs
• Processo FAPESP: 14/12401-2 - Supercondutividade ná solução sólida (Nb1-xZrx)B
• Beneficiário: Fábio Santos Alves Abud
• Linha de fomento: Bolsas no Brasil - Mestrado