High-temperature soft magnetic properties of Co-doped nanocrystalline alloys

In situ hysteresis measurements were used to follow the evolution of soft magnetic properties of various Co containing Finemet- and Hitperm-type nanocrystalline materials. This work is aimed at obtaining the proper chemical composition of nanocrystalline alloys, which can be applied for highest temperatures and is less affected by the inevitable decoupling phenomena, which is common to all two-phase nanocrystalline systems. Experimental results pointed out that in the Co-added Finemet-type alloys the decoupling temperature can be increased by about 50–70 K as compared to Co-free Finemet alloy. Hitperm alloys, close to equiatomic Fe/Co ratio, have much higher decoupling temperature, but their coercivity is an order of magnitude larger at low temperatures compared to the Co-free alloys so their advantage is evident above 400 °C only.