Rolling-induced texturing in metal-clad MgB2 tapes and magnetoresistivity anisotropy

Abstract

Metal-clad MgB2 tapes with Cu, Ni, Fe, and stainless steel sheaths, fabricated by the powder-in-tube method, have been studied using x-ray diffraction and magnetoresistance measurements. Tapes subjected to different mechanical and thermal processings have been used to probe the ab-plane texturing. Only moderate rolling-induced texturing has been observed experimentally, with a maximal texture factor, ΔF00l, of about 0.22. ΔF00l is found to be dependent on both the sheath material and tape processing prehistory. Electrical resistivity measurements in high magnetic fields (parallel and perpendicular to the tape plane) show that even poor texturing, with ΔF00l=0.065, may result in a significant anisotropy of magnetoresistance. The anisotropy of the upper critical field, Bc2, has been derived from the experimental texturing and magnetoresistance data, with the anisotropy factor of the order 5 at 4.2K. It is shown that a maximal magnetic field shift of the resistively probed superconducting transition associated with the tape core texturing may reach 4.5T at 4.2K.

Anisotropy of the critical current in MgB2tapes made of high energy milled precursor powder

“…The largest anisotropy value of 10 at 8 T was found here at tapes with a Ti-sheath. Also Beilin [6] came in principle to similar results. Rolled tapes exhibit a clear increase in the intensity of (001) peaks, which depends on the sheath material (hardness .…”

Critical currents in weakly texturedMgB2: Nonlinear transport in anisotropic heterogeneous media

“…the distribution function of the relevant transport property (e.g., the critical current density J c ) depends on its orientation. This is realized in weakly (or partially) textured MgB 2 and explains the J c -anisotropy 4,5,6,7,8,9,10,11,12 , which can exceed the intrinsic anisotropy of MgB 2 (5-6) 13 by orders of magnitude. The J c -anisotropy can be induced by some preparation techniques of MgB 2 tapes, which was impossible in the conventional superconductors NbTi and Nb 3 Sn since they are intrinsically isotropic.…”

Superconducting MgB2 textured bulk obtained by ex situ spark plasma sintering from green compacts processed by slip casting under a 12 T magnetic field

“…The asprocessed samples showed enhancement of the critical current density (J c ). More articles on partially oriented MgB 2 and anisotropy of superconducting properties were reported for powder-in-tube tapes [21][22][23][24][25][26][27]. These tapes were produced both by ex situ [21,25] and in situ [26,27] routes.…”