Experimental research on electric field jump in low magnetic fields: Detection of damage in new ex-situ MgB₂ barriers in MgB₂ wires

We explored the incorporation of field sweep (constant current and rapidly increasing magnetic field) into the four-probe method as a new technique to detect defects in barrier layers in superconducting MgB₂ wires. This method allows us to observe jumps in the electric field in low magnetic fields. The scanning electron microscopy results indicate that such a jump originates from cracks in Nb barriers and ex-situ MgB₂ barriers. Our research indicates that the field sweep allows us to detect damage to barriers that are made of superconducting materials. This method can be the basis for an industrial method for detecting damages in MgB₂ wires. These defects reduce the critical current of MgB₂ wire. Detection and removal of these defects will allow us to produce MgB₂ wires with ex-situ MgB₂ and Nb barriers that will have improved critical current density. Manufacturing of MgB₂ wires with new ex-situ MgB₂ barriers is a new technological concept. This type of barrier is cheaper and easier to manufacture, leading to cheaper MgB₂ wires. Moreover, we show that critical current can be measured by two methods: current sweep (constant magnetic field and quickly increasing current) and field sweep. - Graphical abstract: Our results indicate that the jump electric field low magnetic fields. This jump indicates damage in Nb and ex situ MgB₂ barrier. Detection and removal of defects will increase J_c in MgB₂ wires and will increase the applicability of MgB₂ wire. - Highlights: • Jump electric field in the 1 T indicates damage to the Nb barrier. • Jump resistance at 9 K indicates damage to the Nb barrier. • Jump electric field in low magnetic field indicates damage to ex situ MgB₂ barrier. • Damage Nb and ex situ MgB₂ barrier significantly reduces the critical current density in the MgB₂ wire