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Comparative Study of Dense Bulk MgB$_2$ Materials Prepared by Different Methods

V. N. Narozhnyi·G. Fuchs·A. Handstein·A. Gümbel·J. Eckert·K. Nenkov·D. Hinz·O. Gutfleisch·A. Wälte·L. N. Bogacheva·I. E. Kostyleva·K. -H. Müller·L. Schultz
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Abstract

We report on the results of a comparative investigation of highly dense bulk MgB$_2$ samples prepared by three methods: (i) hot deformation; (ii) high pressure sintering; and (iii) mechanical alloying of Mg and B powders with subsequent hot compaction. All types of samples were studied by ac-susceptibility, dc-magnetization and resistivity measurements in magnetic fields up to $μ_0H=160$ kOe. A small but distinct anisotropy of the upper critical field $H_{c2}^{a,b}/H_{c2}^{c}\sim1.2$ connected with some texture of MgB$_2$ grains was found for the hot deformed samples. The samples prepared by high pressure sintering as well as by mechanical alloying show improved superconducting properties, including high upper critical fields $H_{c2}$ ($μ_0H_{c2}(0)\sim23$ T), irreversibility fields $H_{irr}$ which are strongly shifted towards higher values $H_{irr}(T)\sim0.8H_{c2}(T)$ and high critical current $J_c$ ($J_c=10^5$ A/cm$^2$ at 20 K and 1 T).

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V. N. Narozhnyi, G. Fuchs, A. Handstein, A. Gümbel, J. Eckert, K. Nenkov, D. Hinz, O. Gutfleisch, A. Wälte, L. N. Bogacheva, I. E. Kostyleva, K. -H. Müller, L. Schultz. 2002-06-26. Comparative Study of Dense Bulk MgB$_2$ Materials Prepared by Different Methods. https://doi.org/10.1023/a%3A1021211628080

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