Peak Effect Induced by Heavy-ion Irradiation in 2H-NbSe2 Single Crystals

Peak effect has been studied in 2H-NbSe2 single crystals with splayed columnar defects introduced by 320 MeV Au irradiation. Through the magnetic relaxation experiments, correspondence between the peak effect and magnetic relaxation has been observed. However, by calculating the critical current density (Jc) much before the first measurement using a SQUID magnetometer based on the relaxation rate S, it is found that the peak effect is present even at the very early stage of relaxation, indicating that it is caused by the magnetic field dependence of pinning force.