• Journal of Powder Materials
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• v.28 no.6
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• pp.509-517
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• 2021

Smart materials capable of changing their characteristics in response to stimuli such as light, heat, pH, and electric and magnetic fields are promising for application to flexible electronics, soft robotics, and biomedicine. Compared with conventional rigid materials, these materials are typically composed of soft materials that improve the biocompatibility and allow for large and dynamic deformations in response to external environmental stimuli. Among them, smart magnetic materials are attracting immense attention owing to their fast response, remote actuation, and wide penetration range under various conditions. In this review, we report the material design and fabrication of smart magnetic materials. Furthermore, we focus on recent advances in their typical applications, namely, soft magnetic actuators, sensors for self-assembly, object manipulation, shape transformation, multimodal robot actuation, and tactile sensing.

• Electrical & Electronic Materials
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• v.9 no.1
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• pp.76-92
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• 1996

본 고에서는 대표적인 연자성재료인 Soft 페라이트, 퍼멀로이, 센더스트와 비정질 자성합금계의 특성과 용도를 살펴봄으로써 현재의 기술현황을 알아보고 그 문제점 해결과 특성개선을 위한 연구동향에 대하여 검토하여 보기로 한다. 또한 연자성재료 일반에 걸쳐 용도별 분류와 각 응용기술 분야에서의 기술동향 및 전망에 대하여 소개하고자 한다.

• Journal of Magnetics
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• v.16 no.4
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• pp.403-407
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• 2011

Metal-insulator type, nano-granular soft magnetic films have been reviewed from the viewpoint of high frequency magnetic materials. The formation of nano-granular structure is related to the magnitude of heat of formation of intergranule materials. Variation of the ratio of granule phase to intergranule phase in the film is found to produce various characteristics in the magnetic properties of the film. The HRTEM observation reveals that neighboring granules in the film with above 60 at.% Co, contact at considerable points and the films show soft magnetic properties which are explainable in terms of the random anisotropy model for nano-crystalline materials. Addition of Ni group elements in Co-O based films enhances their anisotropy field up to 400 Oe and they exhibit excellent frequency response of permeability. Also, large electromagnetic noise suppression effect is demonstrated as one of their potential applications.

• Journal of Powder Materials
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• v.28 no.3
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• pp.233-238
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• 2021

Iron-based amorphous powder attracts increasing attention because of its excellent soft magnetic properties and low iron loss at high frequencies. The development of an insulating layer on the surface of the amorphous soft magnetic powder is important for minimizing the eddy current loss and enhancing the energy efficiency of high-frequency devices by further increasing the electrical resistivity of the cores. In this study, a hybrid insulating coating layer is investigated to compensate for the limitations of monolithic organic or inorganic coating layers. Fe₂O₃ nanoparticles are added to the flexible silicon-based epoxy layer to prevent magnetic dilution; in addition TiO₂ nanoparticles are added to enhance the mechanical durability of the coating layer. In the hybrid coating layer with optimal composition, the decrease in magnetic permeability and saturation magnetization is suppressed.

• Journal of Magnetics
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• v.22 no.1
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• pp.29-33
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• 2017

We report a micromagnetic numerical study on different quasi-crystal formations of magnetic vortices in a rich variety of dynamic transient states in soft magnetic nano-disks. Only the application of spin-polarized dc currents to a single magnetic vortex leads to the formation of topological-soliton quasi-crystals composed of different configurations of skyrmions with positive and negative half-integer numbers (magnetic vortices and antivortices). Such topological object formations in soft magnets, not only in the absence of Dzyaloshinskii-Moriya interaction but also without magnetocrystalline anisotropy, are discussed in terms of two different topological charges, the winding number and the skyrmion number. This work offers an insight into the dynamic topological-spin-texture quasi-crystal formations in soft magnets.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.6
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• pp.401-415
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• 2021

Soft robots are promising devices for applications in drug delivery, sensing, and manufacturing. Traditional hard robotics are manufactured with rigid materials and their degrees of motion are constrained by the orientation of the joints. In contrast to rigid counterpart, soft robotics, employing soft and stretchable materials that easily deforms in shape, can realize complex motions (i.e., locomotion, swimming, and grappling) with a simple structure, and easily adapt to dynamic environment. Among them, the magnetic actuators exhibit unique characteristics such as rapid and accurate motion control, biocompatibility, and facile remote controllability, which make them promising candidates for the next-generation soft robots. Especially, the magnetic actuators instantly response to the stimuli, and show no-hysteresis during the recovery process, essential for continuous motion control. Here, we present the state-of-the-art fabrication process of magnetically controllable nano-/micro-composites, magnetically aligning process of the composites, and 1-dimensional/multi-dimensional multimodal motion control for the nextgeneration soft actuators.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1173-1174
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• 2006

Improvement of the strength is one of the most important subjects on soft magnetic composite (SMC) to increase the applica ble items. In this study, lubricants for inner lubricating SMC, which can be produced in lower cost than die wall-lubricatin g SMC, varied to investigate their effect on the strength. The newly developed SMC with self-lubricating resin shows high st rength equivalent to that of SMC obtained by die wall lubrication.

• Journal of the Korean Magnetics Society
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• v.21 no.2
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• pp.77-82
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• 2011

The use of soft magnetic materials have been increasing in the various industrial fields according to the increasing demand for high performance, automatic, miniaturing equipments in the recent our life. In this study, we investigated the effect of factors on the core loss and magnetic properties of electrical steel and soft magnetic composites. Furthermore, we reviewed the major efforts to reduce the core loss and improve the soft magnetic properties in the two main soft magnetic materials. Domain purification which results from reduced density of defects in cleaner electrical steels is combined with large grains to reduce hysteresis loss. The reduced thickness and the high electrical conductivity reduce the eddy current component of loss. Furthermore, the coating applied to the surface of electrical steel and texture control lead to improve high permeability and low core loss. There is an increasing interest in soft magnetic composite materials because of the demand for miniaturization of cores for power electronic applications. The SMC materials have a broad range of potential applications due to the possibility of true 3-D electromagnetic design and higher frequency operation. Grain size, sintering temperature, and the degree of porosity need to be carefully controlled in order to optimize structure-sensitive properties such as maximum permeability and low coercive force. The insulating coating on the powder particles in SMCs eliminates particle-to-particle eddy current paths hence minimizing eddy current losses, but it reduces the permeability and to a small extent the saturation magnetization. The combination of new chemical composition with optimum powder manufacturing processes will be able to result in improving the magnetic properties in soft magnetic composite materials, too.

• Proceedings of the Korean Magnestics Society Conference
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• 2014.05a
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• pp.57-57
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• 2014

• Korean Journal of Materials Research
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• v.14 no.11
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• pp.780-785
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• 2004

The degradation mechanism of soft magnetic properties of $Fe-Hf-N/Cr/SiO_2$ thin films reacted with a bonding glass was investigated. When $Fe-Hf-N/Cr/SiO_2$ films were annealed under $600^{\circ}C$ without the bonding glass, the compositions and the soft magnetic properties of Fe-Hf-N layers were not changed. However, after reaction with the bonding glass at $550^{\circ}C$, the soft magnetic properties of the film were degraded. At $600^{\circ}C$, the saturation magnetization of the reacted film decreased to 13.5 kG, and its coercivity increased to 4 Oe, and its effective permeability decreased to 700. It was founded that O diffused from the glass into the Fe-Hf-N layers during the reaction and generated $HfO_2$ phases. It was considered that the soft magnetic properties of the $Fe-Hf-N/Cr/SiO_2$ films reacted with the bonding glass were primarily degraded by the formation of the Fe-Hf-O-N layer of which the Fe content was below 60 $at\%$, and secondarily degraded by the Fe-Hf-O-N layer above 70 $at\%$.