The Magnetic Properties of The Alloys Fe(Al, Mn) System

In this thesis we study the magnetic properties of the alloy system Fe(Al1-xMnᵪ), for x=0.31 , 0.35 , 0.60 and 0.80,by measuring the susceptibility in the temperature range 300 <= T <= 650 K° in very small ac magnetic field. The analysis of the susceptibility curves show that the sample with x=0.31 is paramagnetic, while the samples with x=0.35, 0.60 and 0.80 are ferromagnetically ordered. The susceptibility for x=0.31 obeys the Curie-Weiss law with a negative paramagnetic temperature (ɵp= -144K) and shows nearly a straight line with nearly the same susceptibility during all the process. For the other samples (with x=0.35, 0.60 and 0.80) show the coexistence of ferromagnetic and antiferromagnetic behavior with Neel temperature (Tn)= 335, 387 and 393 K and with paramagnetic temperature ɵp=g 340,393 and 425 K respectively. It is clear that the sample with x=0.31 exhibits only one paramagnetic phase, but for the other samples, two phases exist; antiferromagnetic phase below Neel temperature and paramagnetic phase above Neel temperature. The Fe(Al1-xMnᵪ) alloy system is very sensitive to temperature and the measured values for both susceptibility and Neel temperature during heating do not coincide with those values during cooling.