Intermixing of Fe and Cu on the atomic scale by high-pressure torsion as revealed by DC- and AC-SQUID susceptometry and atom probe tomography

TL;DR

This study explores how high-pressure torsion creates supersaturated Cu-Fe solid solutions with nanocrystalline grains, revealing atomic-scale mixing, magnetic properties, and phase evolution through advanced microscopy and susceptometry.

Contribution

It demonstrates the atomic-scale intermixing of Fe and Cu via high-pressure torsion and correlates microstructural and magnetic changes with thermal treatment.

Findings

Enhanced Fe solubility in Cu after high-pressure torsion

Presence of superparamagnetic and frustrated magnetic phases in as-deformed state

Magnetic frustration vanishes after annealing at 250°C

Abstract

The capability of high-pressure torsion on the preparation of supersaturated solid solutions, consisting of Cu-14Fe (wt.%), is studied. From microstructural investigations a steady state is obtained with nanocrystalline grains. The as-deformed state is analyzed with atom probe tomography, revealing an enhanced solubility and the presence of Fe-rich particles. The DC-hysteresis loop shows suppressed long range interactions in the as-deformed state and evolves towards a typical bulk hysteresis loop when annealed at 500{\deg}C. AC-susceptometry measurements of the as-deformed state reveal the presence of a superparamagnetic blocking peak, as well as a magnetic frustrated phase, whereas the transition of the latter follows the Almeida-Thouless line, coinciding with the microstructural investigations by atom probe tomography. AC-susceptometry shows that the frustrated state vanishes for annealing at 250{\deg}C.