Progressive magnetic softening of ferromagnetic layers in multilayer ferromagnet-nonmagnet systems and the role of granularity

TL;DR

This study investigates how the magnetic properties of the top ferromagnetic layer in Co-Au multilayers soften progressively due to increased amorphization, supported by experimental and simulation data.

Contribution

It reveals the progressive magnetic softening linked to structural amorphization in multilayer systems, combining experimental and micromagnetic simulation insights.

Findings

Increased amorphization of the top layer with more bilayers.

Decreased magnetic hardness and anisotropy with amorphization.

Micromagnetic simulations support experimental observations.

Abstract

We report a study of the structural and magnetic behavior of the topmost magnetic layer in a ferromagnet-nonmagnet (Co-Au) multilayer system. Glancing angle X-ray diffraction measurements performed on a series of multilayers showed a gradually increasing degree of amorphization of the topmost magnetic layer with increasing number of bilayers. Concurrently, the magnetic hardness and magneto-crystalline anisotropy of the top Co layer were found to decrease, as observed by magneto-optical Kerr effect measurements. This magnetic softening has been discussed in the light of Herzer's random anisotropy model. Micromagnetic simulations of the multilayer system also corroborated these observations.