Temperature dependence of irreversible switching fields in NdFeB exchange-spring ribbons

The aim of this work is to study the evolution with measurement temperature of magnetic interactions in those phases precipitated after the crystallization of amorphous ribbons of Nd4.5Fe72Co3Cr2Al1B17.5 produced by melt-spinning. Different annealing temperatures were attempted to obtain well-coupled magnetic nanostructured phases to boost remanence and energy product. 57Fe Mössbauer spectroscopy experiments and FORC diagrams at different temperatures were performed. For the overaged ribbons, the diagrams at lower temperatures display a dramatic reduction in the intensity of irreversible interactions. In agreement with Mössbauer spectroscopy results, this fact confirms that soft and hard magnetic phases are weakly coupled in this system.