Oblique angle deposited FeCo multilayered nanocolumnar structure: Magnetic anisotropy and its thermal stability in polycrystalline thin films.

[Display omitted] • The present work describes a unique method to form the multilayer by combining oblique angle deposition (OAD) and normal angle deposition (NAD), to achieve strong magnetic anisotropy along with better high thermal stability in polycrystalline films. • Depositing several thin FeCo layers in between normally deposited FeCo layers, a strong uniaxial magnetic anisotropy (UMA) is produced in a thick FeCo multilayer structure; otherwise, FeCo is magnetically isotropic. • This method is applicable for any nanostructured magnetic material of polycrystalline or amorphous nature, where magnetocrystalline anisotropy is absent due to the absence of long-range structural order. • The present study provides a new method to produce a thin-film layered structure using single material with controlled morphology. This may have prominent implications for future technological devices, including optical devices or any kind of radiation absorbing devices where use of any single material is required, etc. Iron-Cobalt (FeCo) columnar, multilayered structure is prepared by depositing several thin FeCo layers by varying the angle between the surface normal and the evaporation direction as 0° (normal) and 60°(oblique), alternatively. In situ X-ray scattering and magneto-optical Kerr effect (MOKE) measurements established the evolution of magnetic properties with that of the morphology and structure of the multilayer. The strong shape anisotropy and compressive stress of nanocolumns in alternative FeCo layers resulted in a well-defined uniaxial magnetic anisotropy (UMA) with the easy axis of magnetization along the projection of the tilted nanocolumns in the film plane. The stress in the film provides minimization of magnetoelastic energy along the in-plane column direction, which couples with the columnar shape anisotropy energies and results in the preferential orientation of the magnetic easy axis along the oblique angle deposition direction in the film plane. Drastic reduction in the in-plane UMA after annealing at 450 °C is attributed to the merging of columns and removal of stresses after heat treatment. The present study opens a new pathway to produce magnetically anisotropic multilayer structures using single material and thus may have prominent implications for future technological devices. [ABSTRACT FROM AUTHOR]