First-principles study of Fe2VAl and Fe2VAl/Si thin films and their magnetic properties

We studied thin films of Fe2VAl, Fe2VAl/Si, and a related compound using the total energy pseudopotential method. The internal atoms in a supercell of the repeated slab model were fully relaxed, except for Fe2VAl/Si. The detailed electronic and magnetic properties of structurally relaxed thin films of Fe2VAl, Fe2VAl/Si, and a related compound were calculated. These films are free-standing in the supercell, except for Fe2VAl/Si, which comprises Fe2VAl and Si (substrate) layers in a supercell. A thin film comprising Fe2V, Al, and Si (substrate) layers in the supercell (denoted as Fe2V/Al/Si) was also studied. Although electronic states of bulk Fe2VAl (full-Heusler) are metallic with pseudo-gap states around the Fermi level and nonmagnetic, the calculation results for Fe2VAl, Fe2VAl/Si, and Fe2V/Al/Si thin films in this study indicate that the films have ferromagnetic properties and their ferromagnetic states are energetically more favorable than nonmagnetic states. The magnetic moments are large and enhanced in the thin films. The magnetic moments of Fe in Fe2VAl (Fe12V4Al4), Fe2VAl (Fe20V8Al8), Fe2VAl/Si, and Fe2V/Al/Si thin films are 2.07 μB/per atom, 1.29 μB/per atom, 1.83 μB/per atom, and 2.22 μB/per atom, respectively. Although thin films have net ferromagnetic properties, the magnetic moments of the up and down spin states of Fe and V are antiferromagnetically aligned.