Phase diagram of multi-layer ferromagnet system with dipole-dipole interaction

TL;DR

This study explores the magnetic configurations in thin-film ferromagnets with dipole-dipole interactions, revealing five typical states and their metastability, influenced by boundary conditions and anisotropy.

Contribution

It provides a detailed analysis of magnetic states and metastability in dipole-interacting thin films, highlighting the formation of a concentric canted multi-domain pattern.

Findings

Identified five typical magnetic configurations including vortex and multi-domain states.

Discovered the formation of a concentric canted multi-domain pattern due to boundary conditions.

Compared metastability of out-of-plane ferromagnetic and vortex states.

Abstract

We investigate various magnetic configurations caused by the dipole-dipole interaction (DDI) in the thin-film magnet with the perpendicular anisotropy under the open boundary conditions. Two different approaches are simulated: one starts from a random magnetic configuration and decreases temperatures step-wisely; the other starts from the saturated out-of-plane ferromagnetic state to evaluate its metastability. As typical patterns of magnetic configuration, five typical configurations are found: an out-of-plane ferromagnetic, in-plane ferromagnetic, vortex, multi-domain, and canted multi-domain states. Notably, the canted multi-domain forms a concentric magnetic-domain-pattern with an in-plane vortex structure, resulting from the open boundary conditions. Concerning to the coercivity, a comparison of the magnetic configurations in both processes reveals that the out-of-plane ferromagnetic state exhibits metastability in the multi-domain state, while not in the vortex state. We also confirm that the so-called Neel-cap magnetic-domain-wall structure, which is originally discussed in the in-plane anisotropy system, appears at the multi-domain state.