Magnetic Properties of Rapidly Quenched Soft Magnetic Co-Based Alloy Subjected to Heat Treatment in a Sulfur Atmosphere

The effect of heat treatments (HTs) in a sulfur atmosphere of a rapidly quenched soft magnetic 71KNSR (Co72Ni12.2Fe5.7Si6.5B3.6) alloy on its magnetic properties is studied in this work. The alloy under study is subjected to HTs at temperatures above and below its Curie temperature. It is shown that the magnetic properties are improved in both cases. It is likely that the improvement is traceable to the relaxation of internal quenching stresses in the course of heat treatment. X-ray diffraction studies performed after HT in a sulfur atmosphere at 350°С showed up the appearance of cobalt sulfide, which can inducing additional tensile stresses. This results in a decrease in the volume of domains with the magnetization perpendicular to the ribbon plane, which, in turn, explains the more substantial improvement of the magnetic properties of the Co72Ni12.2Fe5.7Si6.5B3.6 ribbon after HT in the sulfur atmosphere at the temperature above the Curie temperature.