Abstract
Current magnetic memories are based on writing and reading out the domains with opposite orientation of the magnetization vector. Alternatively, information can be encoded in regions with a different value of the saturation magnetization. The latter approach can be realized in principle with chemical order-disorder transitions in intermetallic alloys. Here, we study such transformations in a thin-film (35 nm) Fe60Al40 alloy and demonstrate the formation of periodic magnetic nanostructures (PMNS) on its surface by direct laser interference patterning (DLIP). These PMNS are nonvolatile and detectable by magnetic force microscopy (MFM) at room temperature after DLIP with a single nanosecond pulse. We provide different arguments that the PMNS we observe originate from increasing magnetization in maxima of the interference pattern because of chemical disordering in the atomic lattice of the alloy at temperatures T higher than the critical temperature Tc for the order (B2)-disorder (A2) transition. Theoretically, our simulations of the temporal evolution of a partially ordered state at T>Tc reveal that the disordering rate is significant even below the melting threshold. Experimentally, we find that the PMNS are erasable with standard thermal annealing at T<Tc.
Highlights
IntroductionChemical order-disorder transformations in intermetallic alloys[1,2,3,4,5,6,7,8,9,10] such as FexAl100-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
We find that the formed periodic magnetic nanostructures (PMNS) are clearly detectable with magnetic force microscopy (MFM) at room temperature
We find that a single-pulse direct laser interference patterning (DLIP) treatment provides the formation of the PMNS which consists of alternating bright and dark spots in the MFM images
Summary
Chemical order-disorder transformations in intermetallic alloys[1,2,3,4,5,6,7,8,9,10] such as FexAl100-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. The question arises whether the chemically disordered state can survive upon cooling the alloy to temperatures T below the critical temperature Tc 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. The goal of our study is to produce small nonvolatile magnetic structures[19,20] by focusing laser irradiation on the sample surface. In these experiments we employed direct laser interference patterning (DLIP) which allows for fabrication of large-area
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