In-plane and out-of-plane magnetoresistance in La2-xSrxCuO4 single crystals.

Abstract

The magnetoresistance of ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CuO}}_{4}$ single crystals has been studied extensively over a wide composition range (0.07\ensuremath{\le}x\ensuremath{\le}0.28) using current parallel (in plane) and perpendicular (out of plane) to the ${\mathrm{CuO}}_{2}$ plane. In the underdoped superconducting phase (x\ensuremath{\sim}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\ensuremath{\le}x\ensuremath{\le}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 ${\mathrm{\ensuremath{\tau}}}_{\mathrm{tr}}$ and ${\mathrm{\ensuremath{\tau}}}_{\mathit{H}}$. In the out-of-plane magnetoresistance, we find an unconventional scaling \ensuremath{\Delta}${\mathrm{\ensuremath{\rho}}}_{\mathit{c}}$/${\mathrm{\ensuremath{\rho}}}_{\mathit{c}}$\ensuremath{\propto}(H/${\mathrm{\ensuremath{\rho}}}_{\mathit{a}}$${)}^{2}$ for H\ensuremath{\perp}J and (H/T${)}^{2}$ for H\ensuremath{\parallel}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. \textcopyright{} 1996 The American Physical Society.