Magnetic properties of amorphous, crystalline, and liquid Ni-B alloys

Abstract

From a comprehensive study of the magnetic properties of amorphous and liquid ${\mathrm{Ni}}_{100\ensuremath{-}x}{\mathrm{B}}_{x}$ alloys with $18.5<~x<~40,$ the individual contributions to the magnetization are identified and determined separately. The matrix of the amorphous Ni-B alloys is found to exhibit Pauli paramagnetism even for $x=18.5,$ where the observed magnetization was dominated by superparamagnetic particles. The Pauli susceptibility decreases monotonically with increasing B-content and, for a given composition, it agrees well with extrapolated room-temperature liquid state data and with the value of the corresponding crystalline stoichiometric compound. The critical concentration for the onset of spontaneous magnetic order is established to be more than 81.5-at. % Ni. On the basis of the electronic density of states (DOS) deduced from previous low-temperature specific-heat measurements for various Ni-metalloid alloys, the Stoner-enhanced Pauli susceptibility is calculated for the Ni-B system and a good agreement with the experimental conduction electron susceptibility is obtained. The temperature dependence of the Pauli susceptibility is also discussed for amorphous Ni-B alloys and for liquid Ni-metalloid alloys, the features being explained in terms of the DOS data.