Magnetic properties of the FexMn0.600-xAl0.400, 0.200 ≤ x ≤ 0.600, disordered alloy series

The magnetic properties of the FexMn0.600-xAl0.400 (0.200 less than or equal to x less than or equal to 0.600) disordered alloys were investigated by means of Mossbauer spectrometry, ac magnetic susceptibility, and ac calorimetry measurements. Our results are summarized in a magnetic phase diagram, which includes an antiferromagnetic phase for x less than or equal to 0.300 at T less than or equal to 225 K, a ferromagnetic one for x greater than or equal to 0.425 at T less than or equal to 340 K, and a paramagnetic phase for high temperatures and all the compositions. This phase diagram also shows for the first time both a re-entrant spin-glass-ferromagnetic transition line for x greater than or equal to 0.425 and T less than or equal to 60 K and a re-entrant spin-glass-antiferromagnetic one for x less than or equal to 0.300 and T less than or equal to 40 K. The occurrence of superparamagnetic-like blocked events (for 0.300 less than or equal to x less than or equal to 0.600 and at T approximate to 200 K) is associated with the presence of Fe-rich magnetic clusters which can originate from the disordered atomic character of the alloys.