Magnetic phase transition in (Fe,Mn)65Ni35 alloys

Abstract Magnetization measurements on the Fe 60 Mn 5 Ni 35 and Fe 50 Mn 15 Ni 35 alloy samples were carried out in the temperature range 80⩽ T ⩽300 K and in magnetic fields up to 8 kOe. The Fe 60 Mn 5 Ni 35 was found to order ferromagnetically with a Curie temperature, T c , above 300 K. From the temperature dependence of the spontaneous magnetization, M s , it was concluded that the magnetic behavior of Fe 60 Mn 5 Ni 35 follows Wohlfarth theory of weak itinerant ferromagnet. The Fe 50 Mn 15 Ni 35 sample exhibits a magnetic phase transition from ferromagnetism to paramagnetism at T c =242 K. The critical amplitudes and critical exponents ( β , γ and δ ) have been determined by using Arrott plots, Kouvel–Fisher method and scaling plots of the reduced magnetization and reduced magnetic field. The values of β , γ and δ are discussed and compared with the results obtained for various theoretical models and also with the experimentally determined values for related systems obtained by others.