  Mono- and multifilamentary MgB2/Fe tapes and wires with high transport
critical current densities have been prepared using the powder-in-tube (PIT)
process. The fabrication details are described. The effect of powder grain
sizes and recrystallization temperature on jc has been investigated. At 25K and
1 T, jc values close to 105 A/cm2 were measured, while jc of 106 A/cm2 were
extrapolated for 4.2K/0T in our monofilamentary tape. MgB2/Fe tapes exhibit
high exponential n factors for the resistive transition: n ~ 80 and 40 were
found at 5 T and 7 T, respectively. The highest transport jc values obtained so
far in MgB2/Fe wires with 7 filaments were 1.1 * 105 A/cm2 at 4.2 K and in a
field of 2 T, which is still lower than for monofilamentary tapes. Improved
deformation and recovering processing is expected to lead to higher jc values.
