Coexistence of three structural and magnetic states of Fe in rapidly quenched samples: epitaxy effects in granular solids

Abstract

Coexistence of three well-defined magnetic states of Fe and its correlation with structure is analysed as a function of Fe content in FeCuNi melt spun ribbons. The granular structure of the samples enables to reproduce in bulk state similar studies about the influence of volume expansion on the reinforcement of ferromagnetism in FCC Fe, to those extensively performed in epitaxial FCC Fe thin films. In these granular samples, the evolution of the interface area between the magnetic precipitates and the non-magnetic Cu rich matrix, mainly determines the magnetic nature of the metastable FCC Fe phases. The results show that the equilibrium BCC Fe phase dominates the magnetic state in the sample with higher Fe content (Fe 65Cu 30Ni 5). However, two additional metastable Fe phases, with expanded volume with respect to the BCC equilibrium phase and magnetic moment per atom of 2.8 and 0.8 μ B, are detected for samples with lower Fe content (Fe 25Cu 70Ni 5 and Fe 45Cu 50Ni 5). The evolution of both FCC metastable Fe phases with thermal treatments is correlated with parallel changes of structure and magnetic moment observed in epitaxial FCC Fe thin films. The small Ni content was introduced to help the mixture ability of immiscible Fe and Cu.