Anisotropy of W in Fe and Co

The magnetization and magnetic anisotropy of iron-rich Fe-W and W-Co intermetallics and nanostructures are investigated by first-principle calculations. The W atom is antiferromagnetically coupled to nearest neighbor Co atom and interface Fe atom in the case of Fe-W multilayers. The first anisotropy constants are positive, nearly zero, or negative, depending on the atomic structures. Typical anisotropy energies per atom are -0.513 meV for a dilute W-Co alloy, -0.06 meV for W₂Fe₂, and 0.44 meV for W₂Fe₄ (0.1 meV/atom ~1MJ/m³). These values are of interest for permanent-magnet applications but also indicate the need for careful structural control and for a more detailed investigation of structure-property relationships in Fe-W nanostructures.