Negative Magnetoresistance of Bi_2Sr_2CuO_x Single Crystals in a Strong Magnetic Fields

TL;DR

This study investigates the negative magnetoresistance in Bi_2Sr_2CuO_x single crystals under high magnetic fields, revealing a spin-related mechanism and tunneling effects between CuO_2 layers in the normal state.

Contribution

It provides new insights into the spin-dominated negative magnetoresistance and the activated tunneling behavior in high-temperature superconductor crystals.

Findings

Negative MR up to 60% observed in normal state

MR is independent of current direction at low temperatures

Magnetic field suppresses magnetic fluctuations in CuO_2 planes

Abstract

Magnetoresistance (MR) in the out-of-plane resistivity $\rho_c$ for the normal state of the one-layer high-quality Bi_2Sr_2CuO_x single crystals under various dc magnetic fields up to 28 T over the temperature region 6-100 K has been measured. We observed the anomalously large negative longitudinal MR up to 60%. At low temperatures the normal-state MR in contrast to the MR in mixed state is independent of the direction of the current relatively to the field direction suggesting uniquely the spin dominated origin of that. The magnitude of the MR is activated in magnetic field and temperature. We interpret the activated form of $\rho_c$ and the negative MR in terms of 2D stacked alternating metallic and dielectric layers assuming the tunneling between CuO_2 planes. If the main fluctuations inside CuO_2 planes have magnetic origin, the magnetic field suppresses these fluctuations leading to the uniform spin orientation. In this case the interlayer current will be enhanced well.