The role of one-dimensional magnetic nanoprecipitates on the magnetoresistance of soft magnetic alloys: Study of a melt-spun Cu-Co alloy

This work has investigated the microstructure and magnetic properties of supersaturated melt-spun Cu?10%Co alloys by means of magnetization, magnetotransport studies, electron microscopy and electron holography. Our results demonstrate that the microstructure of the annealed supersaturated alloys is constituted by two different types of Co-rich phases: spherical Co-rich precipitates as a result of spinodal decomposition, and Co rod-like precipitates, as a result of discontinuous grain-boundary precipitation. The aspect ratio of such precipitates is quite high, exhibiting magnetic anisotropy along their long axes, which generates global anisotropy of the alloy sample. We verified that the highest giant magnetoresistance occurs concurrently with an optimum discontinuous precipitate development. Electron holography reveals an antiferromagnetic coupling of the Co rods in the remanent magnetization state. The magnetization and magnetoresistance curves as a function of applied magnetic field are well described by an independent-moment approach considering the sum of the average magnetic moments of the spherical and the rod-like Co precipitates.

Automated summary

The microstructure of annealed supersaturated Cu-10%Co alloys consists of Co-rich spherical precipitates and Co rod-like precipitates. These precipitates exhibit magnetic anisotropy and contribute to the global anisotropy of the alloy. Giant magnetoresistance is highest during optimal discontinuous precipitate development. Electron holography shows antiferromagnetic coupling of Co rods in the remanent magnetization state.