Phase-Change Magnetic Memory: Rewritable Ferromagnetism by Laser Quenching of Chemical Disorder in Fe60Al40 Alloy

Abstract

In systems that store data magnetically, the information can be corrupted by external magnetic fields and by thermal fluctuations. One possible approach, which could solve both of these problems, is altering reversibly the magnetization magnitude instead of its direction. The authors propose such an alternative magnetic memory upon the basis of chemical order-disorder transformations in Fe-Al alloys. It is found out that room-temperature ferromagnetism in Fe 60 Al 40 thin-fim (≈40 nm) samples is recoverable after rapid resolidification of the alloy, which follows its irradiation by a short laser pulse with intensity sufficient for melting.

Direct laser interference patterning of nonvolatile magnetic nanostructures in Fe60Al40 alloy via disorder-induced ferromagnetism

“…The produced samples were post-annealed at 770 K in a vacuum furnace for times 10 3 s and then slowly cooled. After such a treatment, the samples did not have a detectable magnetic response at room temperatures 18 . It was also shown with X-ray diffraction 18 that the annealed films were structurally ordered and that the average diameter of crystalline grains in them was about L=15 nm.…”

“…Chemical order-disorder transformations in intermetallic alloys [1][2][3][4][5][6][7][8][9][10] such as Fe x Al 100-x and their effects on the physical properties [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] attracted steady interest through decades. In particular, the phenomenon of disorder-induced ferromagnetism [11][12][13][14][15][16][17][18][19][20] was extensively studied by employing various kinds of treatments that effectively induced the structural transitions from the chemically ordered (B2) to disordered (A2) state. The performed experiments were supported by theoretical studies [21][22][23][24] that pointed out the enhancement of magnetic moments in the Fe x Al 100-x (50 at.% <x<75 at.%) under the transformation from the B2 to A2 state.…”

“…The performed experiments were supported by theoretical studies [21][22][23][24] that pointed out the enhancement of magnetic moments in the Fe x Al 100-x (50 at.% <x<75 at.%) under the transformation from the B2 to A2 state. Therefore, the question arises whether the chemically disordered state can survive upon cooling the alloy to temperatures T below the critical temperature T c for the A2B2 transition 18,20 . This issue is especially relevant at the nanoscale, when precipitates of a new phase can be still smaller than the critical nucleus for the phase transformation.…”

“…This issue is especially relevant at the nanoscale, when precipitates of a new phase can be still smaller than the critical nucleus for the phase transformation. At a macroscopic scale, writing of nonvolatile ferromagnetism was experimentally demonstrated with Fe 60 Al 40 thin-film specimens under their irradiation by short-pulse laser beam 18 . The goal of our study is to produce small nonvolatile magnetic structures 19,20 by focusing laser irradiation on the sample surface.…”

“…Analyzing these findings in terms of chemical order-disorder transitions, we compare the experimental data with our simulations of the disordering/reordering rates. These studies can be useful in a view of a magnetic memory technology which would encode information in regions with different values of the magnetization saturation 18,32 . Such an approach would be an alternative to current magnetic memory technology where information bits are domains with opposite orientation of the magnetization vector.…”