Magnetic susceptibility studies of amorphous Ni-Mn-P-B-Al alloys

Magnetic susceptibility studies have been made on amorphous (Ni1−xMnx)75P16B6Al3 alloys in the temperature range 4–300 K. In the case of the x = 0 alloy, the mass susceptibility is quite small, ∼10−8 m3/kg at room temperature. With the addition of Mn to x = 0.2, the susceptibility increases to ∼5×10−7 m3/kg. The susceptibility does not change appreciably with the composition from x = 0.2 to x = 0.4. With the further addition of Mn to x = 0.6, the room temperature susceptibility increases to ∼3×10−6 m3/kg. The x = 0.2 alloy shows a broad peak in susceptibility at ∼28 K and a shifted hysteresis loop at 4 K upon field cooling, behavior associated with spin glasses and mictomagnets. The shifted hysteresis loops are unstable at 4 K and shift back toward the origin upon cycling the field. Time dependent effects are also seen at 4 K. These results are interpreted in terms of a continuous freezing of small paramagnetic clusters as the temperature is lowered.