Impact of annealing temperature on magnetic microstructure of Fe80Zr4Ti3Cu1B12 rapidly quenched alloy

Rapidly quenched amorphous Fe80Zr4Ti3Cu1B12 (numbers indicate at.%) alloy was exposed to heat treatments in vacuum resulting in formation of a nanocrystalline structure with varying amounts of bcc-Fe grains. Mِssbauer effect measurements were performed at 300 and 77 K. An onset of crystallization was observed after annealing at 435 °C for 1 h. Analyses of Mِssbauer spectra corresponding to nanocrystalline specimens revealed a presence of three structurally distinct regions: amorphous residual phase, crystalline phase, and interface zone. Evolution of these components and their hyperfine interactions which correlate with magnetic microstructure are studied by distributions of hyperfine magnetic fields. Magnetic regions develop in the retained amorphous phase with rising temperature of annealing. They are undergoing notable changes due to segregation of Fe atoms into bcc nanograins. Consequently, variations in the chemical short-range order are observed as a function of: (a) varying number of nanograins in the samples studied, and (b) temperature of measurement. Measurements of magnetic properties evidenced that partially crystallized samples exhibit high saturation magnetic flux density as well as high permeability. Moreover, low core losses and good frequency stability is observed.