Nanosurface-confined anisotropic growth and magnetism of ellipsoidal alpha-Fe nanogranules

We have investigated the nanosurface-confined anisotropic growth of ordered-ellipsoidal Fe nanogranules when an Fe plume was deposited at a slanting angle onto an anodized aluminum oxide (AAO) film. Layer-by-layer growth was also investigated. This growth is driven by two critical factors: (1) a new rhombic AAO cell and (2) the slanting deposition of the Fe plume. During slanting deposition, the rhombic AAO cell induces strong restrictions in the nucleation site, growth direction, and granular size; therefore, the degree of freedom during growth is restricted. The magnetic dipoles of the ordered Fe nanogranules are placed along the long axis of the ellipsoid at an angle of 180 degrees (antiparallel) due to the demagnetizing field, shape anisotropy, and magnetic dipole-to-dipole interactions.