Resistivity tensor correlations in the mixed state of electron-doped   superconductor Nd$_{2-x}$Ce$_x$CuO$_{4+\delta}$
  The magnetic-field dependencies of the longitudinal and Hall resistance of the electron-doped compounds Nd$_{2-x}$Ce$_x$CuO$_{4+\delta}$ in underdoped region with $x$=0.14 and with varying degrees of disorder ($\delta$) were investigated. It was established experimentally that the correlation between the longitudinal electrical resistivity and the Hall resistivity can be analyzed on the basis of scaling relationships: $\rho_{xy}$($B$)$\sim$ $\rho^{\beta}_{xx}$($B$). For the totality of the investigated single-crystal films of Nd$_{2-x}$Ce$_x$CuO$_{4+\delta}$/SrTiO$_3$ the universal value $\beta$=1.5 $\pm$0.4 is found. The observed feature in the electron-doped two-dimensional systems can be associated both with a displaying of anisotropic $s$ - wave or $d$-wave pairing symmetry and with a rather strong pinning due to an essential degree of disorder in the samples under study. 
T.B. Charikova, N.G. Shelushinina, G.I. Harus, D.S. Petukhov, O.E.   Petukhova, A.A. Ivanov
cond-mat.supr-con