Magnetization ground states and phase diagrams for a nano-sized Co hollow sphere : an onion-type magnetization state

TL;DR

This study investigates the magnetization ground states of nanosized Co hollow spheres, revealing an onion-type state and phase diagrams influenced by anisotropy, finite temperature, and crystalline structure through micromagnetic simulations.

Contribution

The paper introduces an analytical expression for the onion-type magnetization state and maps phase diagrams for different crystalline structures of Co hollow spheres.

Findings

Identification of an onion-type ground state in Co hollow spheres

Phase diagrams showing the influence of anisotropy on magnetization states

Discussion of temperature effects and magnetization reversal properties

Abstract

The magnetization ground states (MGSs) for a nanosized Co hollow sphere, with the outer radius, R < 50 nm, have been studied numerically by micromagnetic simulation using object oriented micromagnetic framework (OOMMF). In addition to the originally known single domain and vortex-curling states, a three dimensional "onion" state with a corresponding analytical expression is proposed and confirmed as one of the ground states. Two phase diagrams, one for a single crystalline and the other for a polycrystalline nanosphere, are obtained for the three MGSs. The result reveals that the magnetic anisotropy has a significant effect on the phase line in the diagrams. The finite temperature effect and the blocking properties of the nanosphere for the magnetization reversal are discussed.