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

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, ΔF₀₀₁, of about 0.22. ΔF₀₀₁ 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 ΔF₀₀₁=0.065, may result in a significant anisotropy of magnetoresistance. The anisotropy of the upper critical field, B_c2, has been derived from the experimental texturing and magnetoresistance data, with the anisotropy factor of the order 5 at 4.2 K. It is shown that a maximal magnetic field shift of the resistively probed superconducting transition associated with the tape core texturing may reach 4.5 T at 4.2 K.