Tuneable Magneto-Resistance by Severe Plastic Deformation

TL;DR

This study demonstrates how severe plastic deformation can be used to systematically tune the magneto-resistance in bulk metallic samples by controlling composition and processing parameters, revealing new ways to optimize magnetic properties.

Contribution

It introduces a simple production method to systematically study and tune magneto-resistance in metallic alloys through processing parameters and composition control.

Findings

Low ferromagnetic content leads to isotropic resistance drop.

Higher ferromagnetic content causes anisotropic magnetoresistance.

Adjusting deformation parameters tailors giant magneto-resistance magnitude.

Abstract

Bulk metallic samples were synthesized from different binary powder mixtures consisting of elemental Cu, Co, and Fe using severe plastic deformation. Small particles of the ferromagnetic phase originate in the conductive Cu phase, either by incomplete dissolution or by segregation phenomena during the deformation process. These small particles are known to give rise to granular giant magnetoresistance. Taking advantage of the simple production process, it is possible to perform a systematic study on the influence of processing parameters and material compositions on the magneto-resistance. Furthermore, it is feasible to tune the magnetoresistive behavior as a function of the specimens chemical composition. It was found that specimens of low ferromagnetic content show an almost isotropic drop in resistance in a magnetic field. With increasing ferromagnetic content, percolating ferromagnetic phases cause an anisotropy of the magnetoresistance. By changing the parameters of the high pressure torsion process, i.e., sample size, deformation temperature, and strain rate, it is possible to tailor the magnitude of giant magneto-resistance. A decrease in room temperature resistivity of approx. 3.5% was found for a bulk specimen containing an approximately equiatomic fraction of Co and Cu.