Magnetic properties of a glassy Ni81.5B18.5 alloy

The amorphous Ni81.5B18.5 alloy prepared by rapid quenching has been studied by magnetization measurements up to 50 kOe and by 11B nuclear magnetic resonance. The magnetization of this alloy is dominated by ferromagnetic component saturating above 20 kOe at about 2 emu/g at 4.2 K and contains also a linear term with a temperature-independent susceptibility of about 3×10−6 emu/g. From the combined magnetic and 11B NMR studies it could be concluded that the observed ferromagnetism may be attributed to the presence of small magnetic particles (amounting to about 2 to 3% of the sample volume) which are embedded in a paramagnetic Ni–B amorphous matrix. These data indicate that for a homogeneous Ni–B system the critical concentration for the appearance of ferromagnetism should be below 19 at.% B.