FLUX PINNING MECHANISM IN NEW MgCNi3 SUPERCONDUCTOR

The measurements of lower-critical-field Hc1(T), upper-critical-field Hc2(T) and the bulk pinning force Fp(H) were carried out for a superconductor MgCNi3 sample with Tc=7.5K prepared under high pressure. The sample has a good extensibility. We conclude that the flux pinning at lower fields results from the intra-granular structural defects, such as dislocations, and the enhancement of bulk pinning force near the irreversibility field Hirr is due to the softening of the flux lattice.