Temperature and field dependence of the magnetization of Fe–Al powders in cold-worked and annealed state

Abstract

Magnetic behaviour of unannealed and annealed Fe‐Al powders has been investigated as a function of field and temperature in the concentration range 0 to 50 at% Al. The magnetization M of unannealed powders (measured at 20 K) decreases monotonously with increasing Al contents up to 30 at% according to a dilution law; at higher Al contents the magnetization decrease is stronger than by magnetic dilution and vanishes at about 50 at% Al. The magnetization of annealed powders already vanishes at about 38 at% Al. M vs. T curves of annealed powders (30 to 36 at% Al) show a maximum at 150 to 250 K. This maximum does not occur in corresponding unannealed powders.

Formation and ordering of local magnetic moments in Fe–Al alloys

“…5), we obtain that those for the AFM solutions are in a better agreement with the experimental data than those in the FM solutions, especially at Al concentrations higher than 35-40 at% (zero magnetic moment per Fe atom obtained for ordered alloys in Ref. [22]). Fig.…”

“…We should note that the SSW wavelength obtained both by us and in Rhombes and triangles denote the AFM and FM, respectively, first-principles results (the data are for the equilibrium lattice parameters), squares are for the experimental data from Ref. [22,23]. Star shows the average moment calculated here from the high-temperature superparamagnetic behavior obtained in experiments in Ref.…”

“…[23] obtained by extrapolation of magnetization from high magnetic fields, Ref. [22], and the average moment calculated in the previous section from the high-temperature superparamagnetic behavior experimentally obtained in Ref. [15].…”

Ordering effects in the Fe-Al system

“…In the high concentration range Jo and Akai [43] [40,49]. The magnetic behaviour is consistent with the observation of Gengnagel et al [36] (who have cooled very slowly their sample from 1000 OC to room temperature) and with the observation of Wakiyama [35] who obtained a saturation magnetic moment per Fe atom of 1.87 JlB.…”

“…The magnetic behaviour depends strongly upon the phase state and upon the atomic arrangement i.e. ordered, partially ordered or disordered structures [2,32,33,36,38,39,42,49,19]. at % Al (after Allen [27] The specific heat has been reported by Beck et a1.…”