Assessment of magnetic properties and structural evolution of nanostructured (Fe30Cu70)96B4 alloys

Abstract

(Fe30Cu70)96B4 (FCB) alloys were produced in an induction furnace and then reduced in size by mechanical milling in stainless steel vials in an Ar atmosphere. Structural, morphological, and magnetic characterization techniques were used to investigate the evolution of powder alloys as a function of their milling time (0, 12, 24, 36, 48, and 60 h). Structural analysis by X-ray diffraction confirmed that all samples exhibit a crystalline fcc structure and space group Fm-3 m. As the milling time increases, the induced stress increments, leading to changes in the lattice parameter value and atomic volume. Thus, lattice parameter values are approximately in the range a = 0. 3614–0.3626 nm. TEM analysis confirmed that after 12 h of milling, the FCB system was made up of nanoparticles with diameters between 6 and 8.2 nm. ZFC-FC measurements revealed that the samples are ferromagnetic at room temperature. Nevertheless, due to the particle's nanometric size, a superparamagnetic-like behavior was evidenced with a blocking temperature (TB) below 60 K. M(H) loops were fitted using a distribution of Langevin functions, obtaining a maximum saturation magnetization Ms ~ 25 emu/g after 24 h of milling. Likewise, the FCB system is magnetically soft a room temperature with coercive field values below (132 Oe). Finally, Mössbauer spectroscopy showed that the superparamagnetic-like behavior could be associated with the Cu matrix's nanoparticle size and Fe atom behavior.