Critical data of niobium nitride in transverse magnetic fields

Critical fields and critical currents of a great number of niobium nitride samples with and without different amounts of zirconium have been measured. The samples for these measurements have been prepared by diffusion of nitrogen into heated niobium and niobium-zirconium wires under various conditions. For the zero upper critical field of NbN the extrapolated value (153±3) kOe has been found. The quenching curves of most of the samples show very pronounced peak effects in the high field region with a steep slope close to the upper critical field, which decreases with increasing amount of zirconium.