Geometric effects in cylindrical core/shell hard–soft exchange-coupled magnetic nanostructures

Namkyu Kim,Hee-Sung Han,Sooseok Lee,Min-Ji Kim,Dae-Han Jung,Myeonghawn Kang,Hyejin Ok,Youngkyun Son,Sukbin Lee,Ki-Suk Lee

doi:10.1016/j.jmmm.2020.167599

Namkyu Kim, Hee-Sung Han + Show 8 more

Open Access

https://doi.org/10.1016/j.jmmm.2020.167599

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Abstract

We explore the optimal condition for cylindrical core/shell hard-soft exchange-coupled magnetic nanostructures by obtaining full hysteresis loops for various geometries by obtaining full hysteresis loops for various geometrical variables, including the dimensional scale and soft/hard-magnetic phase volume ratio through micromagnetic simulations. For achieving maximum energy product (BH), it is essential to increase the demagnetizing field by increasing the volume fraction of the soft magnet while maintaining a positive nucleation field and, which can be possible by the scaling-down. To scale up the nanostructure to a bulk magnet having high BH can be achieved by forming an array of needle-shaped exchange-coupled cylinders. These findings could lead to the flexible design and scalable fabrication of exchange-coupled permanent magnets.

Highlights

Devices such as electric vehicles and wind power generators utilize the magnetic energy of permanent magnets [1,2]
Ex change hardening is inversely proportional to t; when the volume of the soft-magnetic phase is increased by increasing t, the shape anisotropy becomes more dominant than exchange hardening
We explored various geometries of cylindrical core/shell hard–soft exchange-coupled magnetic nanostructures via micromagnetic simula tions to obtain a high energy product, BH

Summary

Introduction

Devices such as electric vehicles and wind power generators utilize the magnetic energy of permanent magnets [1,2]. Cylindrical core/shell microstructure [13,20,24,26] has been presented for high energy product value and for high nucleation field. Despite such intensive theoretical and experimental works, the optimal. We performed micromagnetic simulations on core/shell hard–soft exchange-coupled magnetic cylinder with various geometrical parameters and wide-ranging volume ratios of the hard-to-soft phase, and rigorously evaluated the BH values at a working point considering the demagnetizing field, which is determined by shape. We examined the effects of scaling and the aspect ratio of the shape on arrays of exchange-coupled cylinders, with consideration of the shape of the array structure

Simulation method

Results

Conclusions