Anomalous Non-Linear to Linear Shift in Magnetoresistance of Amorphous Carbon Films

Awais Siddique Saleemi,M Aurang Zeb Gul Sial,Shahid Mehmood,Muhammad Hussan,Shern-Long Lee,Shafiq Ur Rehman,Muhammad Saeed,Muhammad Hafeez

doi:10.3390/cryst9120618

Awais Siddique Saleemi, M Aurang Zeb Gul Sial + Show 6 more

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https://doi.org/10.3390/cryst9120618

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Abstract

Non-linear to linear negative magnetoresistance (MR) was studied under the magnetic field ranging from −7 T to 7 T with a change in measurement temperature from 2 K to 300 K. Under the magnetic field of 7 T, a maximum MR magnitude of 8.2% was observed at 2 K. The chemical vapor deposition technique was adopted to synthesize the amorphous carbon thin films. Non-saturated and non-linear negative MR was observed for the lower temperatures, while 10 K was observed as transition temperature. Afterwards, the more likely linear MR behavior was observed up to 300 K. MR shape change was correlated with the structural morphology of metallic disordered graphitic layers or the random stacking of graphene layers with amorphous carbon. The negative MR mechanism for such a non-linear to linear shift was partially assumed as a combined effect of the diffused scattering theory and the weak localization theory. The negative MR effect has a direct relation with the degree of structural order.

Highlights

In recent days, one of the most important issue in spintronics is to study the magneto-transport phenomenon in magnetic nanostructures
Negative MR of both the reported samples was decreased as the temperature was phenomenon
We explored the shift of MR from non-linear to linear MR with respect to the change in measurement temperature

Summary

Introduction

One of the most important issue in spintronics is to study the magneto-transport phenomenon in magnetic nanostructures. Magnetic nanoparticles have attracted great attention owing to the interaction between the electrical charging effect and spin-dependent tunneling [1,2,3]. These magnetic nanoparticles can be deposited onto insulating substrates, where nanometer-sized magnetic metal particles were confined in the films, and are responsible for giant magnetoresistance (MR). Different allotropes of carbon might contain distinctive bonding configurations and the hybridization is mainly dependent on the four valance electron orbitals. The four-fold symmetry C(sp3 ) hybridization and three-fold symmetry C(sp2 )

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