Critical current density and pinning behaviour of mono-core MgB2 wires prepared by internal magnesium diffusion and in-situ powder-in-tube method.

Mono-core MgB 2 wires were produced by internal magnesium diffusion (IMD) and in-situ powder-in-tube (PIT) technique. Hysteresis loops and magnetic relaxations were measured to calculate critical current density, J cm (via Bean’s critical state model) and mean effective activation energy (via Anderson’s flux creep theory). To calculate J cm of the IMD sample, the formulae for typical cylindrical sample geometry must have been modified properly with regard to IMD hollow cylinder geometry. Results for J cm were compared to direct transport measurements. Also studied was the irreversibility field, B irr , and upper critical field, B c2 . It was found that the dominant difference between wires is in J c . For the IMD sample, J c was higher and less field-dependent than J c of the PIT sample. [ABSTRACT FROM AUTHOR]