Magnetic properties and thermal stability of (Fe,Co)-Mo-B-P-Si metallic glasses

Abstract

A series of ferromagnetic metallic glasses with compositions (Fe,Co)78Mo1(B,P,Si)21 are shown to possess good thermal stability and soft magnetic performance. The thermal stability inside the supercooled liquid temperature region was evaluated using Kissinger analysis of primary crystallization, time-temperature-transformation (TTT) diagrams, and the extent of the supercooled liquid region (ΔTx). The phosphorus-free alloy, Fe78Mo1B15Si6, had an activation energy (Ea) of 414 kJ/mol, ΔTx ∼ 50 K, and began devitrifying after about 1 min at 730 K. By way of comparison, the phosphorus-containing alloy, Fe78Mo1B13P6Si2, had an Ea of 440 kJ/mol, ΔTx ∼ 45 K, and began devitrification after 10 min at 730 K. High saturation magnetization (μ0Ms ∼ 1.45-1.55 T) and low coercivity (Hc ∼ 20 A/m) are demonstrated across the composition range. Core loss measurements of toroidal cores are shown to be less than 12 W/cm3 at 1 T, maximum induction amplitude (under both sinusoidal and square waveforms). Trends were established for magnetic and thermal stability as a function of metalloid and magnetic transition metal composition.