Study of history effect of vortex matter by AC susceptibility

We have observed numerically the history effect, based on bulk flux pinning framework, in the susceptibility chi (T) (acs), experimentally measured in different samples. The dependencies of history effect in chi (T) on freque ncy, ac and dc fields, and bulk pinning strength are calculated. Our calcul ation matches well the behavior of chi in 2H-NbSe2, showing the bulk model works well. It is also shown that bulk pinning and surface pinning will res ult in a history effect of very different characteristics. In addition, the numerical result shows that a peak in critical current density, which is u sually accompanied by the vortex melting transition, may not be observed as a dip in acs in some cases, which is a dynamic response of a sample to app lied as field and is dependent on ac field frequency and amplitude.