MAGNETIC-PROPERTIES OF ELECTRODEPOSITED, MELT-QUENCHED, AND LIQUID NI-P ALLOYS

A comprehensive study of the magnetic properties of Ni100-xPx alloys prepared by electrodeposition with 11.5 less-than-or-equal-to x less-than-or-equal-to 23.2 and by melt quenching with 16.3 less-than-or-equal-to x less-than-or-equal-to 21.0 was performed for temperatures 4.2 less than or similar to T less-than-or-equal-to 300 K in magnetic fields up to H = 9 kOe and, for most of the melt-quenched alloys, for T greater-than-or-equal-to 300 K including the molten state as well. The individual contributions to the magnetization were identified and determined separately. The matrix of Ni-P alloys was found to exhibit Pauli paramagnetism for x greater than or similar to 17 and very weak itinerant ferromagnetism for x less than or similar to 14. However, magnetic inhomogeneities in the form of ferromagnetic precipitates, giant-moment paramagnetic clusters and/or superparamagnetic particles could be identified throughout the whole concentration range studied and their amount and character varied significantly with alloy composition and preparation technique. In the paramagnetic phase, the temperature-independent Pauli susceptibility was not sensitive to the way of preparation, it agreed well with extrapolated room-temperature liquid-state data, decreased approximately linearly with increasing P content and extrapolated to the corresponding value of the crystalline stoichiometric compound Ni3P. In the ferromagnetic phase, the magnetization data of the matrix could be reasonably well accounted for in terms of the Stoner-Edwards-Wohlfarth model and the theory of Mathon, yielding 85.7 at. % Ni as the critical concentration for the onset of spontaneous magnetic order. For alloys in the intermediate composition range (14 less than or similar to x less than or similar to 17), the observed magnetization was dominated by the contribution of superparamagnetic particles.