Superconducting properties with highfield peak effect in ohmicallyheated jellyrolled Nb₃AI wire

Jellyrolled NbyVI wires with a Nb matrix have been ohmicallyheated at controlled maximum temperatures ranging from 1600 to IOUOt in vacuum, in order to investigate the properties of pinning force densities at high magnetic fields. The samples were 1,34 mm diameter and 50 mm long. To obtain the stoichioinetric composition of the A15 phase, each sample was quenched in vacuum after ohmicheating. Critical currents have been measured up to 23 T by a four probe method. The critical temperature of the sample heated at 1940t WAS 18.3 K. In longitudinal crosssections, the samples heated at maximum temperatures less than 1940"C have layer structures consisting of Nbrich regions and A15 phase regions. In the sample heated up to 1940t:, which is the melting point of NbjAI, these layers were not observed. This sample showed a remarkable peak effect in the critical current at high magnetic fields, over 20 T.