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Study of upper critical field of superlattices cntaining ferromagnetic layrs

Research Project

Project/Area Number 08640439
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field 固体物性Ⅱ(磁性・金属・低温)
Research InstitutionTohoku University

Principal Investigator

TAKANAKA Kenji  Tohoku University, School of Engineering, professor, 大学院・工学研究科, 教授 (80005321)

Project Period (FY) 1996 – 1997
Project Status Completed (Fiscal Year 1997)
Budget Amount *help
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1997: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1996: ¥1,800,000 (Direct Cost: ¥1,800,000)
Keywordssuperconducter / ferromagnet / superlattice / transition temperature / upper critical field / 臨海磁場 / 超格子超伝導 / 磁性超格子
Research Abstract

There are experimental observations which show d_f dependence of the transition temperature T_c for the superconducting and ferromagnetic superlattices, where d_f is the thickness of the ferromagnetic layr. The transition temperature T_c, in general, decreases monotonically and saturetes with increasing d_f for the fixed superconducting layr. Using the microscopic theory developed by de Gennes and extended by Takahashi and Tachiki, we have made numerical calculations for T_c, which explain the experimental observations (Czech.J.Phys : 66 3219, (1997) ).
The superconducting superlattices are usually characterized by the BCS interaction V,the density of states N,the diffusion constant D and the exchange potential I.In the real systems, the values of the Debye frequency omega_D are different from each metal. Up to now, there is no theoretical investigation of this effect. We have shown that the magnitude of the attractive interaction is given by the BCS interaction and its range by the Debye frequency (J.Phys.Soc.Jpn : 66 3219, (1997) ).
From the fact that the difference of the Debye frequency gives the qualitatively similar effect on T_c and H_<c2> as that of the BCS coupling constant, we have investigated the upper critical field H_<c2> for the superconducting and ferromagnetic superlattices as the functions of N,D and I.For the large potential interaction I,the transition temperature T_c shows nonmonotonic behavior as a functon of d_f. We have shown that this peculiar behavior arises from the appearance of the pi phase of the pair function and calculated spatial variation of the pair function in order to interpret quantitatively the results (Phys.Rev B : (1998) in press).

Report

(3 results)
  • 1997 Annual Research Report   Final Research Report Summary
  • 1996 Annual Research Report
  • Research Products

    (12 results)

All Other

All Publications (12 results)

  • [Publications] K.Kuboya and K.Takanaka: "Superconducting Properties of Superlattices Containing Ferromagnetic Layers" Czechoslovak Journal of Physics. 46. 583-584 (1996)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1997 Final Research Report Summary
  • [Publications] K.Kuboya and K.Takanaka: "Transition Temperature and Uper Critical Field of Superlattices of dirty Superconductors with Different Debye Cut-Off Frequency" J.Phys.Soc.Jpn. 66. 3219-3223 (1997)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1997 Final Research Report Summary
  • [Publications] K.Kuboya and K.Takanaka: "Upper critical field and transition temperature of superconducting/feeromagnetic superlattices" Phys.Rev B. 印刷中. (1998)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1997 Final Research Report Summary
  • [Publications] K.Takanaka, H.Kishi and K.Kuboya: "Angular Dependence of Upper Critical Field" 印刷中. (1998)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1997 Final Research Report Summary
  • [Publications] K.Kuboya and K.Takanaka: "Superconducting Properties of Superlattices Containing Ferromagnetic Layrs." Czechoslovak Journal of Pysics.46. 583-584 (1996)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1997 Final Research Report Summary
  • [Publications] K.Kuboya aud K.Takanaka: "Transition Temperature and Upper Critical Field of Superlattices of dirty Superconductors with Different Debye Cut-Off Frequency." J.Phys.Soc.Jpn.66. 3219-3223 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1997 Final Research Report Summary
  • [Publications] K.Kuboya and K.Takanaka: "Upper critical field and transition temperature of superconducting/ferromagnetic superlattices." Phys.Rev B.(in press).

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1997 Final Research Report Summary
  • [Publications] K.Takanaka, H.Kishi and K.Kuboya: "Angular Dependence of Upper Critical Field." Physica.C.(in press).

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1997 Final Research Report Summary
  • [Publications] K.Kuboya and K.Takanaka: "Superconduting Properties of Superlattices Containing Ferromagnetic Tayers" Czechoslovak Journal of Physics. 46. 583-584 (1996)

    • Related Report
      1997 Annual Research Report
  • [Publications] K.Kuboya and K.Takanaka: "Transition Temperature and Upper Critical Field of Superlattices of dirty Superconductors with Different Debye Cut-Off Frequency" J.Phys.Soc.Jpn.66. 3219-3223 (1997)

    • Related Report
      1997 Annual Research Report
  • [Publications] K.Kuboya and K.Takanaka: "Upper critical field and transition temparature of superconducting/ferromagnetic superlattices" Phys.Rev B. (1998)

    • Related Report
      1997 Annual Research Report
  • [Publications] Koichi Kuboya: "Superconducting Properties of Superlattices Containing Ferromagnetic Layers" Czech.J.Phys.46. 583-584 (1996)

    • Related Report
      1996 Annual Research Report

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Published: 1996-04-01   Modified: 2020-05-15  

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