Magneto-structural correlations in a systematically disordered B2 lattice

Abstract

Ferromagnetism in certain B2 ordered alloys such as Fe _60 Al _40 can be switched on, and tuned, via antisite disordering of the atomic arrangement. The disordering is accompanied by a ∼1 % increase in the lattice parameter. Here we performed a systematic disordering of B2 Fe _60 Al _40 thin films, and obtained correlations between the order parameter ( S ), lattice parameter ( a _0 ), and the induced saturation magnetization ( M _s ). As the lattice is gradually disordered, a critical point occurs at 1 − S = 0.6 and a _0 = 2.91 Å, where a sharp increase of the M _s is observed. DFT calculations suggest that below the critical point the system magnetically behaves as it would still be fully ordered, whereas above, it is largely the increase of a _0 in the disordered state that determines the M _s . The insights obtained here can be useful for achieving tailored magnetic properties in alloys through disordering.

Keywords

• phase transitions
• disorder
• ion beam modifications
• magneto-structural effects