KATARZYNA BLOCH MICROSTRUCTURE AND HIGH-FIELD MAGNETIC PROPERTIES OF FE-BASED BULK AMORPHOUS ALLOYS In this paper the results of the structural and magnetic properties for bulk amorphous alloys Fe65Co10Y5B20 and Fe63Co10Y7B20 were presented. For the structural investigation was performed by X-ray diffractometry and Mossbauer spectroscopy. It was found that investigated samples were amorphous in the as-cast state. The magnetisation was measured within magnetic fields ranging from 0 to 2T using a vibrating sample magnetometer (VSM). On the basis of the hysteresis loops, the saturation magnetization value and the coercive field were determined.The investigation of the ‘magnetisation in the area close to ferromagnetic saturation’ showed that the magnetisation process in strong magnetic fields is connected with point defects and Holstein-Primakoff paraprocess. Analysis of the high-field magnetization curves has facilitated the calculation of the spin wave stiffness parameter.