Magnetotransport properties of granular oxide-segregated CoPtCr films for applications in future magnetic memory technology

TL;DR

This study investigates the magnetotransport properties of granular oxide-segregated CoPtCr films, revealing giant magnetoresistance effects at microscopic scales that could enhance future magnetic memory technologies.

Contribution

It demonstrates the presence of tunnel magnetoresistance in CoPtCr films through combined bulk and point-contact measurements, highlighting potential for high-density magnetic recording.

Findings

Bulk magnetoresistance less than 0.02%

Giant magnetoresistance up to 50,000% at microscopic scale

Magnetoresistance decreases with applied bias

Abstract

Magnetotransport properties of granular oxide-segregated CoPtCr films were studied on both macroscopic and microscopic length scales by performing bulk and point-contact magnetoresistance measurements, respectively. Such a perpendicular magnetic medium is used in state-of-the-art hard disc drives and if combined with magnetoresistive phenomena (for read/write operations) may lead to a novel concept for magnetic recording with high areal density. While the bulk measurements on the films showed only small variations in dc resistance as a function of applied magnetic field (magnetoresistance of less than 0.02 %), the point-contact measurements revealed giant-magnetoresistance-like changes in resistance with up to 50,000 % ratios. The observed magnetorestive effect could be attributed to a tunnel magnetoresistance between CoPtCr grains with different coercivity. The tunneling picture of electronic transport in our granular medium was confirmed by the observation of tunneling-like current-voltage characteristics and bias dependence of magnetoresistance; both the point-contact resistance and magnetoresistance were found to decrease with the applied dc bias.