The estimation of coherence length for electron-doped superconductor Nd$_{2-x}$Ce$_x$CuO$_{4+delta}$

Results of low-temperature upper critical field measurements for Nd$_{2-x}$Ce$_x$CuO$_{4+delta}$ single crystals with various $x$ and nonstoichiometric disorder ($delta$) are presented. The coherence length of pair correlation $xi$ and the product $k_F$$xi$, where $k_F$ is the Fermi wave vector, are estimated. It is shown that for investigated single crystals parameter $k_F$$xi$ $cong$ 100 and thus phenomenologically NdCeCuO - system is in a range of Cooper-pair-based (BCS) superconductivity.