Magnetic properties of amorphous Ni-B alloys

Results of magnetization measurements carried out on rapidly quenched amorphous Ni_1-xBₓ alloys in the temperature range from 4.2 to 300 K in fields up to 15 kOe are presented and discussed. For the alloys with $x=0.308,0.34$, and 0.37, the magnetic susceptibility is found to comprise two contributions: a nonmagnetic contribution arising from the Pauli spin paramagnetism and a magnetic contribution resulting from trace iron impurities and giant nickel moments. The density of states at the Fermi level, N(EF), evaluated from the temperature-independent part of the Pauli paramagnetic contribution, is found to vary linearly with the d-band occupation. By contrast, the amorphous Ni81.6{B}18.4$ alloy exhibits a magnetic behavior which can be completely accounted for in terms of a theory developed for very weak itinerant ferromagnets. Moreover, a comparison of the magnetic properties of this alloy with those observed for other weak itinerant crystalline ferromagnets strongly suggests an Invar-like behavior for the alloy in question.