• 한국자기학회지
• /
• 제5권5호
• /
• pp.824-827
• /
• 1995

Dielectromagnets are permanent magnets made from resin-bonded hard magnetic powders. Magnetic properties of dielectromagnets depend on kind of used hard magnetic materials as chemical compound, shape, size of grain and applied technology. Comparison of advantages and disadvantages of dielectromagnets made from different kind of magnetic powders induced us to try to prepare dielectromagnets from mixture of hard magnetic powders, not only one of them. The purpose of investigation on this kind of dielectromagnets is to find formula to prepare permanent magnets with properties adequate to different kind of electrical motors requirements. As hard magnetic materials we used powders of ferrite, melt-spun ribbon Nd-Fe-B and Alnico. Papers present results of investigation on technology of this kind of dielectromagnets. It shows also influence of kind of mixture and used technology on magnetic properties of dielectromagnets.

• 한국재료학회지
• /
• 제11권10호
• /
• pp.907-911
• /
• 2001

In order to improve the grindability of magnetic abrasive, Fe-WC magnetic abrasives were made by a plasma melting method after ball milling at various times. This study aims to investigate homogeneously distributed hard phases in Fe matrix and strong bonding between the Fe-matrix and the hard phase. According to XRD, SEM and OM observation, Fe-WC magnetic abrasive powders exhibit the best grindability by plasma melting for 30h ball milling. As a result of magnetic abrasive polishing, the surface roughness, R_{max}$ 5.0$\mu\textrm{m}$, before magnetic abrasive polishing, was reduced to R_{max}$ 2.4$\mu\textrm{m}$. The new magnetic abrasive polishing process is thought to be the useful methods for the automation of three dimensional surface polishing.

• 한국자기학회지
• /
• 제5권5호
• /
• pp.687-689
• /
• 1995

Our team works on mixture of hard magnetic materials. As hard magnetic material we used mixture of powders: melt-spun ribbon Nd-Fe-B, ferrite and Alnico. Their different mixtures are basic material for dielectromagnets under our investigation. Main disadvantage of dielectromagnets with Nd-Fe-B alloy powder as a component is a low corrosion resistance. Protection against corrosion is covering dielectromagnets with metallic or organic coating film. The coating film protects dielectromagnets from free particles on the surface and low resistance for mechanical stresses too. The surface of dielectromagnets prepared from mixture of powders if formed by metallic particles - powder of Nd-Fe-B and Alnico, particles of oxide - powder of ferrite and particles of resin - bonding materials. Team work on technology of laying the metallic coating on dielectromagnets prepared from mixture of mentioned powders. Papers show the results of initial investigation on metallic coating technology. It shows influence of type and used technology of the metallic coating film on magnetic properties of dielectromagnets.

• Bulletin of the Korean Chemical Society
• /
• 제28권12호
• /
• pp.2214-2218
• /
• 2007

The effects of bath temperature on electrochemical behavior, alloy composition, crystallographic structure, morphology and the magnetic properties of electrodeposited Co-Pt-W(P) films were investigated. Electrochemical studies show that alloy electrodeposition has been shifted to more positive potentials and the critical time for nucleation decreased as electrolyte temperature increased. As the temperature increased from 40 oC to 80 oC, tungsten content in the deposit increased, while phosphorus content decreased. The films deposited at T = 40 oC exhibited soft magnetic properties. However, electrodeposited at T = 70 oC, the films exhibited hard magnetic properties. It is also demonstrated that higher temperature more than 70 oC could weaken hard magnetic properties. XRD results indicated that the deposits obtained at 50 oC-70 oC showed enhancement of [00.1] P.O. (preferred orientation) with the bath temperature, which resulted in the stronger perpendicular magnetic anisotropy.

• Journal of Magnetics
• /
• 제1권1호
• /
• pp.19-23
• /
• 1996

In the present study, the $Sm_2Fe_{17}N_x$-type interstitial materials have been prepared by reaction between Nb-free or Nb-containing $Sm_2Fe_{17}$-type alloy and $N_2$ gas. Nitrogenation behaviour of the $Sm_2Fe_{17}N_x$-type material and disproportionation characteristics of the nitrogenated materials have been studied by means of differential thermal analysis (DTA) and thermopiezic analysis (TPA). Magnetic properties of the produced $Sm_2Fe_{17}N_x$-type interstitial materials were characterised in vibrating sample magnetometer (VSM) or thermomagnetic analyser (TMA). Epoxy-bonded or Zn-bonded $Sm_2Fe_{17}N_x$-type magnets were prepared, and their magnetic properties were investigated. It has been found that nitrogenation kinetics of the Sm2Fe17Nx-type alloy is improved significantly by the Nb-substitution for Fe in the alloy. The Nb-substitution is also found to enhance thermal stability of the $Sm_2Fe_{17}N_x$-type interstitial material. Hard magnetic properties of the interstitial materials produced from Nb-free orNb-containing alloy is high enough (intrinsic coercivity : over 7 kOe) for application as bonded permanent magnets. The good hard magnetic properties of the interstitial material are maintained in the epoxy-bonded magnet. Intrinsic coercivity of the Zn-bonded magnets is improved significantly as post-bonding annealing time increases.

• Journal of Magnetics
• /
• 제18권3호
• /
• pp.331-338
• /
• 2013

We present a few significant advances in methods and concepts of magnetic measurements, aimed both at providing novel routes in the characterization of hard and soft magnetic materials and at improving our basic knowledge of the magnetization process. We discuss, in particular, investigation methods and experimental arrangements that have been developed in recent times for: 1) Hysteresis loop determination in extra-hard magnets by means of Pulsed Field Magnetometry; 2) Broadband observation of domain wall dynamics by highspeed stroboscopical Kerr techniques; 3) Entropy measurements in magnetocaloric materials by calorimetry in magnetic field. While pertaining to somewhat independent fields of investigation, all these measuring techniques have in common a solid approach to the underlying physical phenomenology and have a potential for further developments.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2017년도 임시총회 및 하계학술연구발표회
• /
• pp.116-116
• /
• 2017

• 한국재료학회지
• /
• 제13권6호
• /
• pp.394-397
• /
• 2003

MTJ devices are fabricated using metal shadow masks and switching characteristics are investigated under 2 dimensional magnetic field. When the hard axis field is less than $\pm$ 16 Oe, switching behavior is similar to that based on the Stoner-Wohlfarth model. As the hard axis field is larger than $\pm$ 16 Oe, deviation from the expectation by Stoner-Wohlfarth model is observed. These phenomena are induced by the generation of multi-domain and inhomogeneous magnetization reversal.

• Applied Microscopy
• /
• 제36권spc1호
• /
• pp.63-69
• /
• 2006

By utilizing a field emission gun and a biprism installed on a transmission electron microscope (TEM), electron holography is extensively carried out to visualize the electric and magnetic fields of nanomaterials. In the electric field analysis, the distribution of electric potential in a sharp tip made of W coated with $ZrO_2$ is visualized by applying the voltage to the tip. Denser contour lines due to the electric potential are observed with an increase in the bias voltage. In the magnetic field analysis by producing the strong magnetic field with a sharp magnetic needle made of a permanent magnet, the in situ experiment is carried out to investigate the magnetization of hard magnetic materials. The results of these experiments clearly demonstrate that electron holography is a promising advanced transmission electron microscopy technique to characterize the electric and magnetic properties of nanomaterials.

• 전기화학회지
• /
• 제8권3호
• /
• pp.125-129
• /
• 2005

본 연구에서는 고순도 알루미늄 호일$(t=300{\mu}m)$양극산화 공정을 통해 AAO 나노템플레이트를 자체 제조하였고, 이렇게 제조된 형틀을 가지고 교류 나노전주법에 의해 경자성 합금인 CoP와 연자성 합금인 CoFe를 나노와이어로 제조하였다. 대표적인 Co계 자성합금인 CoP와 CoFe나노와이어는 각기 독특한 자기적 성질을 나타내었다. 경자성 CoP 합금 나노와이어의 경우 교류 인가전압에 따라 hcp와 fcc가 혼재된 구조가 형성되어 자기적 특성에 영향을 미쳤다. 또한 높은 포화자화 값을 갖는 CoFe연자성 합금 나노와이어는 박막 도금 시와는 달리 이상합금도금현상이 거의 나타나지 않았으며 $Co_{30}Fe_{70}$에서 가장 좋은 238emu/g의 포화자화 값을 나타내었다.