Anisotropic superconducting properties ofMgB2single crystals probed by in-plane electrical transport measurements

Abstract

We report on study of the electronic anisotropy of the newly discovered MgB

Influence of the upper critical-field anisotropy on the transport properties of polycrystalline MgB2

“…It was pointed out recently [12] that this small application range was caused by the upper critical field anisotropy of MgB 2 . In the pure material, B c2 is about 14 T, if the field is applied parallel to the boron planes, while it is smaller than 3 T, if the field is applied perpendicular to the boron planes, leading to an anisotropy of close to 5 [13,14,15,16,17,18]. In polycrystalline MgB 2 , the grains are randomly oriented and the first grains become normal conducting at B ⊥ c2 , which is a few times smaller than the upper critical field of the whole sample (B || c2 ), thus reducing the effective cross section and the critical current of the conductor.…”

Effects of the size of Mg powder on the formation of MgB2and the superconducting properties

“…In addition to a high T c , the MgB 2 superconductor has many advantages for the practical use of the materials. The coherence length of MgB 2 is longer than that of high-T c oxide superconductors [2] and the current anisotropy is smaller [3][4]. The two current properties make it easy to fabricate the MgB 2 superconductor as a bulk or wire form.…”

“…In the reaction process using MgB 4 and Mg powders, the amount of Mg used to form MgB 2 is smaller than the conventional in situ process [21][22][23]. Therefore, the number of pores can be reduced.…”

“…2 shows a histogram of the apparent density of the MgB 2 samples before and after heat treatment. The MgB 2 samples were prepared using MgB 4 and Mg powders of various sizes (A-F). The apparent densities of the pressed pellets using powder B and C (the spherical Mg powders with moderate sizes) are higher than the others; whereas the apparent density of the pressed pellet using powder E (large plate-like Mg powder) is the lowest.…”

“…In this study, MgB 2 bulk superconductors were fabricated by the reaction of MgB 4 and Mg. In the reaction process using MgB 4 and Mg powders, the amount of Mg used to form MgB 2 is smaller than the conventional in situ process [21][22][23].…”