CRITICAL-BEHAVIOR IN 2 REENTRANT NIMN FERROMAGNETS

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 chi' 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 chi". A correlation is established between the reentrant susceptibility peaks and the reentrant phase boundaries predicted by vector spin models for bond disordered systems.