Magnetic properties of ultrasoft-nanocomposite FeAlSiBNbCu alloys

The effects of up to 10 at% substitution of Fe by Al on the microstructure and DC and AC magnetic properties of nanocrystalline FeSiBCuNb alloy ribbon are summarised and analysed. The minimum DC Hc developed during annealing decreases by 40% for 2 at% Al (to 0.3 A/m) and remains roughly constant for larger Al contents. The largest peak value of μ0.4 at 50 Hz also corresponds to 2 at% Al. The best frequency response for μ0.4 occurs for 6 at% Al while there was no improvement in AC power loss behaviour over the 0% Al alloy. The improvements in DC Hc and AC μ0.4 are ascribed to a reduction in K1 of the Fe-Si-based nanocrystallites by the introduction of Al