Title : Geometrical impact on Magnetic Properties of Mesoscopic Scale thick Nickel thin films
A real material thin film never exhibits a perfect or ideal geometrical shape, regardless of its formation conditions. This is mainly depicted by its unavoidable bulk usually represented by its thickness (d≠0) and its surface irregularities commonly considered in term of surface roughness (σ≠0), both film characteristics being closely interconnected. Their individual morphology and microstructure engender different behavior under a particular physical field (E) effect. Any related film’s property (p) always results from their combined contributions. The study of p evolution is commonly investigated through its dependence on d as mainly encountered for macroscopic scale thick samples. However, configuration of real nano-films and nanostructured thin films is specific most of the time. Consequently, the study of their p evolution requires an adapted approach reflecting that specificity.
In the present work, our original proposal is illustrated by the study of nanostructured nickel electrodeposits for which evolution of coercivity (Hc) and magnetic domain size (w) are precisely investigated. It is then clearly demonstrated that only a new film geometrical characteristic (τ) defined as τ = (d/σ) can consistently lead to the announced objective. The study of these properties evolution using the normalization model indicates a discontinuity in the magnetism of the investigated samples. Bloch magnetic domains (MD)B are associated with mixed domain walls (DWN + DWB) below a critical position (τ0 -1) ≈ 0.35, while Néel domain walls (DWN) coexist with mixed magnetic domains (MDB + MDN) beyond that position.