In-plane and out-of-plane magnetoresistance in ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_4$ single crystals

The magnetoresistance of ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Sr}}_{\mathit{x}}$ ${\mathrm{CuO}}_4$ single crystals has been studied extensively over a wide composition range (0.07≤x≤0.28) using current parallel (in plane) and perpendicular (out of plane) to the ${\mathrm{CuO}}_2$ plane. In the underdoped superconducting phase (x∼0.10), the in-plane magnetoconductivity above ${\mathit{T}}_{\mathit{c}}$ is well described as fluctuation conductivity but only with the Aslamasov-Larkin term. The negligibly small Maki-Thompson contribution is suggestive of anisotropic Cooper pairing. We find a pronounced negative and isotropic out-of-plane magnetoresistance at low temperatures in this composition range. In the optimally doped to the overdoped superconducting phases (0.15≤x≤0.20), a substantial normal-state component is observed in the in-plane magnetoresistance. The classical Kohler’s rule appears to break down for the normal-state magnetoresistance, which supports the involvement of two distinct scattering rates ${\mathrm{\tau }}_{\mathrm{tr}}$ and ${\mathrm{\tau }}_{\mathit{H}}$. In the out-of-plane magnetoresistance, we find an unconventional scaling Δ${\mathrm{\rho }}_{\mathit{c}}$/${\mathrm{\rho }}_{\mathit{c}}$∝(H/${\mathrm{\rho }}_{\mathit{a}}$ ${)}^2$ for H⊥J and (H/T${)}^2$ for H∥J. In contrast to these anomalous behaviors, we find that Kohler’s rule holds for both the in-plane and the out-of-plane transverse magnetoresistance in the overdoped normal metal region, implying a conventional anisotropic three-dimensional transport. These findings provide further evidence for the unconventional normal-state transport in the samples which exhibit high-${\mathit{T}}_{\mathit{c}}$ superconductivity. © 1996 The American Physical Society.