Chemical Synthesis of High-Stable Amorphous FeCo Nanoalloys with Good Magnetic Properties

It is difficult to fabricate high-purity amorphous FeCo alloys by traditional physical methods due to their weak glass forming ability. In this work, the fully amorphous FeCo nanoalloys with high purity and good stability have been prepared by a direct chemical reduction of Fe²⁺ and Co²⁺ ions with NaBH₄ as the reducing agent and polyvinylpyrrolidone (PVP) as the surfactant. The morphologies, surface compositions and particle sizes with their distribution of these amorphous samples can be effectively tuned by the suitable PVP additions. High crystallization temperature up to 468 °C, high saturation magnetization of 196.2 A·m²·kg^-1 and low coercivity of 83.3 Oe are obtained in amorphous FeCo nanoalloys due to their uniform distribution, weak surface oxidation and low surface B concentration. Good frequency-dependent magnetic properties can be also achieved in the fully compacted amorphous sample with a high density of 7.20 g/cm³. The simple chemical method, high stability and good magnetic properties for these amorphous FeCo nanoalloys promise their significant potential applications in high-power magnetic devices.