• Journal of the Korean Magnetics Society
• /
• v.26 no.2
• /
• pp.50-54
• /
• 2016

We analyzed the angular dependence of ferromagnetic resonance linewidth in exchange coupled CoFe/MnIr bilayers. The maximum and minimum linewidth was observed in the easy and hard direction of unidirectional anisotropy by exchange coupling, respectively, and it was well agreed with the angular dependence of exchange bias field. The maximum linewidth was due to the twist of CoFe magnetization near CoFe/MnIr interface from direction of pinned MnIr spin to direction of applied magnetic field. While, minimum linewidth more higher than that of CoFe was related to rotatable anisotropy field, and explained by easy axis distribution of MnIr grains.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2001.04a
• /
• pp.42-43
• /
• 2001

• Journal of the Korean Magnetics Society
• /
• v.1 no.2
• /
• pp.42-48
• /
• 1991

The basic soft magnetic characteristics of a typical Fe based amorphous $Fe_{80}B_{15}Si_{5}$ alloy were measured with pulse metheod. Quantitative relations between magnetostriction, anisotropy energy, reluctivity were investigated. The relative contribution factor of magnetostrictive and uniaxial anisotropy energy to the reluctivity were calculated. The internal stress and induced anisotropy were estimated. A tension applied to the long axis of the sample greatly enhanced induced anisotropy.

• Journal of the Korean Magnetics Society
• /
• v.3 no.3
• /
• pp.208-214
• /
• 1993

In order to investigate the origin of an increase in the coercivity with the Ta addition to Co-Cr films, the perpendicular magnetic anisotropy of Co-Cr film and CoCrTa film was measured by a torque magnetometer and VSM. In Co-Cr binary alloy film, the uniaxial anisotropy increased with increasing Cr content. The perpendicular magnetic anisotropy of $Co_{81.7}Cr_{16.7}Ta_{1.6}$ film was larger than that of $Co_{81}Cr_{19}$ film, both of which were deposited at the same substrate temperature of $100^{\circ}C$. The change in the perpendicular magnetic anisotropy with annealing was studied to understand the Ta addition effect. The amount of decrease in perpendicular magnetic anisotropy of the CoCrTa film by the annealing was larger than that of Co-Cr film. And the perpendicular magnetic anisotripies of Co-Cr film and CoCrTa film after annealing were almost the same. The cause of this was interpretated as the enhanced segregation of solute atoms in the Ta added thin film in the as-deposited state. The enhanced segregation of solute atoms increases the perpendicular magnetic anisotropy of the film, and causes the increase of perpendicular coercivity of the film.

• Journal of the Korean Magnetics Society
• /
• v.2 no.2
• /
• pp.125-131
• /
• 1992

기판회전 테이블이 부착된 DC, RF-magnetron sputtering 장치로 유리기판 위에 제작한 1000 .angs. 정도의 8.8 .angs. Tb/X .angs. Fe (X=5.4~11.0) 다층박막에 관하여 시료진동형 자 기계와 타원편광 분석장치를 사용하여 자화, 수직자기이방성, kerr 회전각의 Fe층 두께와 열처리 온도 의존성이 연구되었다. Fe층 두께가 7.8 .angs. 기점으로하여 자화용이축의 전이가 나타나기 시작하여 6.4 .angs. 일때 수직자기이방성을 나타낸다. 실험치로부터 계산한 Fe와 Tb층의 경계면 수직이방성 에너지 $K_{s}$ = -0.38 erg/$cm^{2}$이고, Fe층만의 체적수직이방성 에너지 $K_{v}$ = -8.50 * $10^{5}$ erg/$cm^{3}$이다. Polar Kerr 회전각은 Fe층 두께 7.8 .angs. 에서 그대값 2 .THETA. $_{k}$ = 1.22 .deg. 를 갖는다.다.다.다.

• Journal of the Korean Magnetics Society
• /
• v.12 no.3
• /
• pp.88-93
• /
• 2002

Rapidly solidified NdFeB powders were mixed with fine powders of pure metal elements before CA-press employed to obtain a fully dense isotropic precursor. Subsequently, the precursor was deformed by CA-deformation to obtain an anisotropic magnet. The CA-deformed anisotropic NdFeB magnets with 0.3 wt.% Zn or Sn exhibited the coercivities about 80% higher (11.4. and 11.2 kOe, respectively) than that (6.4 kOe) of the additive-free magnet.

• Journal of the Korean Magnetics Society
• /
• v.2 no.3
• /
• pp.251-256
• /
• 1992

Artificial superlattices of Co/Pd were prepared by RF magnetron sputtering Multilayered structure and compositional modulation were analyzed with a side angle x-ray diffractometer. It has been found that expansion of Co lattice occured in this artificial superlattice due to the lattice mismatch between Co and Pd. Perpendicular magnetic anisotropy could be observed when the Co layer thickness became less than 8${\AA}$ and maximum coercivity of 2350 Oe could be obtained in [Co(2.5 ${\AA}$)/Pd(9.3 ${\AA})]_{50}$/Pd$(200\;{\AA})$ with a perfect squareness of magnetic hysteresis loop. Characteristic of perpendicular magnetic anisotropy in Co/Pd superlattices could be related to the expansion of Co lattice caused by Pd layer and it turned out that as the thickness of Pd layer increased, perpendicular magnetic anisotropy increased. The interface anisotropy energy and volume anisotropy energy were calculated to be 0.29 ergs/$cm^2$ and -$6.9{\times}10^6$ ergs/$cm^3$ respectively, which are consistent with the values reported elsewhere.

• Electrical & Electronic Materials
• /
• v.5 no.3
• /
• pp.329-336
• /
• 1992

본 논문은 이방성 Sr.페라이트의 자기특성의 개선에 관하여 연구한 것이다. 시편은 SrO.nFe$_{2}$O$_{3}$의 기본조성으로서 비화학양론적 영역인 n=5.9를 택하였다. 그리고 보자력을 증가시키기 위하여 기본첨가제로서 0.7wt% CaCO$_{3}$와 0.3% wt% SiO$_{2}$를 첨가하여 하소시킨 다음 $Na_{2}$SiO$_{3}$의 량을 변화시키면서 복합첨가하였다. 한편, 위의 시료(기본첨가제와 0.5wt% $Na_{2}$SiO$_{3}$)에 Cr$_{2}$O$_{3}$ 및 $Al_{2}$O$_{3}$를 단독 및 복합첨가한 결과, 0.5wt% $Al_{2}$O$_{3}$가 단독첨가되었을 경우, 좋은 자기특성을 나타내었다. 본 연구에서 시행한 복합첨가방식에 의한 Sr.페라이트의 자기특성의 조사를 통하여 등방성의 경우, 기본조성과 기본첨가제와 0.5wt% $Na_{2}$SiO$_{3}$와 0.5wt% $Al_{2}$O$_{3}$조성에서 (BH)$_{max}$=1.15MGOe, 그리고 이방성의 경우, (BH)$_{max}$=3.23MGOe를 얻었으며 시료를 이방성화하므로서 자기특성면에서 등방성인 경우의 2~3배의 개선효과를 얻었다. 그리고 소결온도는 1210.deg.C에서 가장 좋은 특성을 나타내었으며 큐리온도는 등방성의 경우 T$_{c}$=410~420.deg.C에서 이방성의 경우 T$_{c}$=439~445.deg.C로서 약 30.deg.C가 향상되었다.

• Journal of the Korean Magnetics Society
• /
• v.4 no.3
• /
• pp.219-225
• /
• 1994

The alignment of Sr-ferrite magnetic powders, which is usually related to the fluidity and the applied magnetic field, is investicated in the anisotropic Sr-ferrite / resin-bonded permanent magnets. The magnetic powder alignment is observed to increase with the applied magnetic field and the fluidity which is a function of molding temperature and powder packing ratio. The best magnetic powder alignment is achieved at the following conditions; Sr-ferrite packing ratio of 56vol%, apparent viscosity of about 3000 poise in $1000sec^{-1}$ shear rate, and applied magnetic field of about 5kOe. The degree of preferred orientation of the magnetic powders in the field direction, as determined by the dc hysterisis graphs, is 84~85% (0.84~0.85). This result is in agreement with the value of 0.85 obtained by the X-ray experiments in the $2{\theta}$ range of ${23~40}^0$. The best magnetic properties obtained are:2.2kG of remanent flux density, 2.2MGOe of maximum energy product.

• Journal of the Korean GEO-environmental Society
• /
• v.12 no.11
• /
• pp.71-77
• /
• 2011

Recently, non-destructive stress measurement method using magnetic anisotropy sensor has been applied to the construction site such as steel bridges and steel pipes. In addition, steel rib used in the tunnel construction site was found to be possible to measure the stress by non-destructive method. In this study, steel loading experiments using magnetic anisotropy sensor developed in Japan and strain gauges were conducted to derive stress sensitivity curve for domestic steel SS400. Also, additional steel loading experiments and numerical analysis were performed for evaluation of applicability for non-destructive stress measurement method using magnetic anisotropy sensor. As a result of this study, stress sensitivity curves for domestic steel SS400 were derived using output voltage measured by magnetic anisotropy sensor and average of stress measured by strain gauges depending on the measurement location. And as a result of comparing additional steel loading experiments with the numerical analysis, error level of magnetic anisotropy sensor is around 20MPa. When considering the level of the yield stress(245MPa) of steel, in case of using magnetic anisotropy sensor in order to determine the stress status of steel, it has sufficient accuracy in engineering. Especially, magnetic anisotropy sensor can easily identify the current state of stress which considers residual stress at steel structure that stress measurement sensor is not installed, so we found that magnetic anisotropy sensor can be applied at maintenance of steel structure conveniently.