Critical behavior in two reentrant N iMn ferromagnets

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Abstract
The real and imaginary components of the low-field dynamic susceptibility of two reentrant NiMn ferromagnets containing 22.5 and 23 at. % Mn have been measured as a function of temperature in static magnetic fields up to 43.3 Oe. The real component χ′ exhibits a triple-peaked structure. A critical analysis confirms the highest temperature component of this structure as a manifestation of the critical fluctuations associated with the paramagnetic–ferromagnetic transition. The remaining double-peaked structure is localized in the vicinity of the reentrant transition and is accompanied by a complementary structure in the imaginary component χ″. A correlation is established between the reentrant susceptibility peaks and the reentrant phase boundaries predicted by vector spin models for bond disordered systems.