Examination of the Field Dependence of the Stoner Enhancement in Pd–Ni Alloys at High Magnetic Fields

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Abstract
The paramagnetic susceptibility χ of the Pd–Ni system is a strong function of Ni concentration; the critical composition for ferromagnetism is somewhat less than 2 at.% Ni. This experimental result can be explained either by a uniform Stoner enhancement which increases with Ni concentration, or by an increased local enhancement in the vicinity of the Ni atoms. This latter concept is also useful in explaining several related exchange‐enhancement dependent properties. To determine which model is correct, measurements of χ were made at 1.4° and 4.2°K in magnetic fields up to 87 kG. The local enhancement model predicts a field dependent Stoner enhancement (χ decreasing as H is increased). This type of field dependence in χ was indeed found at 1.4°K for all the Pd–Ni alloys examined (0.47, 0.97, 1.66, and 3.6 at.% Ni); the strength of the field dependence of χ was found to increase as the Ni concentration increased. At 4.2°K, the 0.47 at.% Ni sample yielded a field independent χ, while for pure Pd, χ was field independent at both temperatures. It was not possible to relate either χ or the magnetic moment to a simple power series in the magnetic field.

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