Formation of structure and magnetic properties of nanostructured bulk Co-based alloys at plasma spray deposition and dynamic compaction

The bulk nanostructured CoFeNi-SiB alloys were prepared by dynamic compaction and plasma spray deposition techniques. The preparation of bulk samples includes several process steps: obtaining of rapidly quenched amorphous ribbon; annealing of ribbon to embrittlement; ribbon grinding in powder; and finally, plasma spraying or dynamic compaction. The investigations of structure and magnetic properties of bulk samples were carried out by X-ray diffraction, electron microscopy and correlation magnetometry. The amorphous/crystalline phase ratio was estimated using the technique of magnetic phase analysis. The effect of processing steps of bulk amorphous alloys preparing on the magnetic characteristics of the samples was investigated. The regimes of dynamic compaction (the loading pressure PLs oC) were selected so that the saturation magnetization, exchange constant, Curie temperature, local anisotropy field, and ferromagnetic resonance linewight of the bulk samples are identical to those of the rapidly quenched Co58Fe5Ni10B16Si11 ribbon. It was found that the bulk materials produced by shock compaction technique as well as plasma spraying technique are nanostructured. A comparison between the magnetic properties of the CoFeNi-SiB alloys prepared by dynamic compaction and a plasma spray deposition techniques was carried out. The analysis of the magnetic hysteresis loops curves shows that plasma spraying does not cause a change of Hc value (0.3 Oe). The coercive field of shock wave compacted sample is slightly bigger than that of the initial ribbon (0.5 Oe).