Effect of Co on the microstructure, magnetic properties and thermal stability of bulk Fe73−xCoxNb5Y3B19 (where x = 0 or 10) amorphous alloys

Abstract

The paper presents the results of structure, thermal stability and magnetic properties of bulk Fe73−xCoxNb5Y3B19 (where x=0 or 10) amorphous alloys in the as-cast state, in the form of 0.5mm thick plates with an area of 100mm2. The amorphous structure of the investigated alloys was confirmed by studies of Mössbauer effect and X-ray diffractometry. On the basis of measurements performed using a vibrating sample magnetometer (VSM), it was found that substituting 10% of Fe with Co in Fe73−xCoxNb5Y3B19 alloy, had only a small effect on the value of saturation magnetization (μ0MS), and was of the same importance in terms of the values of the coercivity field (HC) and the Curie temperature (TC).The magnetization for both samples increases in high magnetic fields due to rotation of magnetic moments near the structural defects called quasidislocalised dipoles, near the area known as the approach to ferromagnetic saturation. For field values with a linear relationship (μ0H)−1 of the reduced saturation magnetization (M/MS), further increase of the magnetization for the studied samples is associated with the Holstein–Primakoff process, which is under the influence of dumping of thermally activated spin-waves.The curves of thermal analysis, obtained using differential scanning calorimetry (DSC), show that Co reduces the glass transition and primary crystallization temperatures.The results of this study indicate that substituting 10% of Fe with Co in ferromagnetic Fe73Nb5Y3B19 alloy causes the deterioration of its so-called soft magnetic properties and decreases the Curie temperature and the primary crystallization temperature.