Angular Dependence of C-Axis Magnetoresistance in Bi-2212 Single Crystals With Columnar Defects

TL;DR

This study investigates how the c-axis magnetoresistance in Bi-2212 single crystals with columnar defects depends on the angle of the applied magnetic field, revealing insights into vortex behavior and pancake alignment.

Contribution

It demonstrates the angular dependence of magnetoresistance and introduces a method to estimate pancake correlation length using a specific crossing point in the data.

Findings

Magnetoresistance scaling breaks near 68 K with in-plane field influence.

Identification of a crossing point at B_cr ≈ B_Phi/2 where magnetoresistance is orientation-independent.

Evidence of enhanced pancake alignment in vortex liquid with columnar defects.

Abstract

We measured the angular dependence of the c-axis magnetoresistance rho_c(B) of Bi-2212 irradiated with heavy ions. At temperatures near 68 K the scaling of rho_c(B) with the c-axis magnetic field component B_perp is broken and the in-plane field, B_parallel, affects rho_c. At this temperature, at a specific field B_cr \approx B_Phi/2, magnetoresistance becomes independent of field orientation. This crossing point allows us to estimate the correlation length L of pancake positions along the c axis. We find L/s is about 100 at B=B_cr, where s is the interlayer spacing. This provides evidence of strong enhancement of pancake alignment in the vortex liquid in crystals with columnar defects.