Abstract. Magnetic properties of Nd₅₀Fe₄₀Si_10-xAl_x (x = 0; 10) melt -spun ribbons with thicknesses between 30 and 150 μm and bulk rods up to 2 mm in diameter prepared by suction casting were investigated in the temperature range 5–600 K. The dependence of the coercive field on the thickness of the sample and the method of preparation is ascribed to the existence in the amorphous matrix of very small ferromagnetic clusters that can not be detected by X-ray diffraction. The coexistence of two types of magnetic order: spin glass short-range order and ferromagnetic long-range order is proved by the specific behaviour of zero-field cooled and field cooled magnetization curves.

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