Observation of vortex phase transition in MgB2 single crystals by a magnetic torque method

T. Nojima, H. Nagano, H. Maruyama, Y. Watanabe, Akira Ochiai, Hayuyoshi Aoki

Research output: Contribution to journalConference articlepeer-review

5 Citations (Scopus)


The magnetic torque measurements were performed on two MgB2 single crystals with the different values of upper critical fields H c2 (3.7 T and 3.1 T at 4.2 K). At low temperatures, the irreversible torque-vs-field curves τ(H) in the both samples show the peak effect, accompanied by the field-history dependence, close to Hc2 for all the field directions measured. With increasing temperature, the peak in τ(H) becomes less pronounced, and disappears around T = 27 K. In the sample with smaller Hc2, τ(H) curves display diamagnetic steps at the higher temperatures. On the other hand, in the sample with larger Hc2, such a step is not observed. Our results suggest that the order-disorder transition around the peak transforms to the first-order melting transition, which is very sensitive to the degree of disorder.

Original languageEnglish
Pages (from-to)163-168
Number of pages6
JournalPhysica C: Superconductivity and its applications
Issue numberI
Publication statusPublished - 2005 Oct 1
EventProceedings of the 17th International Symposium on Superconductivity (ISS 2004) Advances in Supeconductivity -
Duration: 2004 Nov 232004 Nov 25


  • Diamagnetic step
  • MgB
  • Peak effect
  • Single crystal
  • Torque
  • Vortex matter phase diagram

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering


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