Magnetic properties of the Fe_xMn_0.600-xAl_0.400, 0.200 ≤ x ≤ 0.600, disordered alloy series

The magnetic properties of the Fe_xMn_0.600-xAl_0.400 (0.200 ≤ x ≤ 0.600) disordered alloys were investigated by means of Mössbauer spectrometry, ac magnetic susceptibility, and ac calorimetry measurements. Our results are summarized in a magnetic phase diagram, which includes an antiferromagnetic phase for x ≤ 0.300 at T ≤ 225 K, a ferromagnetic one for x ≥ 0.425 at T ≤ 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 ≥ 0.425 and T ≤ 60 K and a re-entrant spin-glass-antiferromagnetic one for x ≤ 0.300 and T ≤ 40 K. The occurrence of superparamagnetic-like blocked events (for 0.300 ≤ x ≤ 0.600 and at T ≈ 200 K) is associated with the presence of Fe-rich magnetic clusters which can originate from the disordered atomic character of the alloys.