• 산업기술연구
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• 제21권A호
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• pp.221-229
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• 2001

The effect of Mo underlayer on the magnetic properties of CoCrTa/Cr films deposited on glass substrates were investigated. The coercivity increased and the coercivity squareness decreased by introducing Mo underlayer. The coercivity increase was attributed to the increase of in-plane c-axis orientation and magnetic isolation of Co grains deposited on Cr/Mo underlayer. The decrease of coercivity squarenesses seemed to be caused by the increase of magnetic isolation. The increase of magnetic isolation of Co grains was attributed to the diffusion of Mo atoms into grain boundaries of Co films and the physical isolation of Co grains. The coercivity of CoCrTa/Cr/Mo showed maximum values at Mo thickness of $400{\AA}$. The appearance of the maximum coercivity at that thickness was attributed to the development of strong $Co(10{\bar{1}}0)$ and $Co(10{\bar{1}}1)$ preferred orientation.

• E2M - 전기 전자와 첨단 소재
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• 제11권10호
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• pp.72-77
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• 1998

The effects of Al micro-bumps on the magnetic properties of CoCr(Pt)Ta/Cr films deposited on glass substrates were investigated. The coercivity increased and the coercivity squareness decreased by incorporating Cr/Al underlayers. The cause of the coercivity increase is attributed to the reduction of Co(0002) texture, the increase of magnetic isolation of CoCr(Pt)/Ta grains, and the refinement of CoCr(Pt)/Ta grains deposited on Cr/Al underlayers. The effects of an Al overlayer on the magnetic properties of CoCr(Pt)Ta/Cr films were also studied. The decrease of coercivity squareness is ascribed to the magnetic isolation of CoCr(Pt)Ta grains.

• 한국재료학회지
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• 제14권8호
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• pp.565-572
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• 2004

The microstructures of variously heat treated hypoeutectoid($0.45\%$ carbon) and eutectoid($0.85\%$ carbon) steel were characterized by magnetic coercivity measurement. The effect of spheroidization of cementites on the coercivity was investigated for $0.45\%$ carbon steel. In case of $0.85\%$ carbon steel, microstructural parameters such as prior austenite grain size, phase and pearlite interlamellar spacing were measured along with coercivity to investigate the relationships between them. Prior austenite grain size had little effect on the measured coercivity. Coercivity was observed to be high in order of martensite, pearlite and ferrite phases. The linear decrease of coercivity with increasing pearlite interlamellar spacing was found. The effect of each microstructural factor on the coercivity and the potential of coercivity as a nondestructive evaluation parameter for assessing microstructures of steel products are discussed.

• 한국자기학회지
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• 제10권6호
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• pp.297-301
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• 2000

보자력은 시편의 자화를 0으로 감소시키기 위해서 필요한 임계 자기장의 세기로 강자성체를 연.경 자성체로 구분하는 기준이 된다. 개방자기회로에서 자성재료의 보자력을 간단히 측정할 수 있는 시스템을 구성하고, 데이터지향언어인 LabVIEW를 사용하여 자기장 제어와 데이터 수집이 가능하도록 하였다. 구성한 보자력 측정 장치의 측정범위는 수십 kA/m에서 수십 kA/m이고, 보자력이 14.63 kA/m일 때 합성표준불확도는 $\pm$0.22 kA/m이다.

• Journal of Magnetics
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• 제4권3호
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• pp.73-75
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• 1999

By appliying an slternate pulsed magnetic field -generated by using a sequential ignition circuit and a magnet exciting circuit- with peak value of about 10 T to the rod type Nd based magnet Nd2Fe12.7Cr1.3B with length of 5 mm and diameter of 3.6 mm, the basic magnetic properties such as saturation magnetization, residual magnetization, coercivity, maximum energy products, magnetic anisotropy and anisotropic field are investigated with obtaining the major and minor J-H loops of the magnet. The increase in coercivity due to eddy currents in ac measurement of coercivity is calculated considering eddy current loss by analyzing a wave of generating magnetic field. The average coercivity calculated for the magnet is about 12.2 kOe, anisotropy magnetic field and anisotropic constant are measured as 60 kOe 2.43 Mj/$m^3$, respectively.

• 한국자기학회지
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• 제5권3호
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• pp.216-221
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• 1995

자성분말의 보자력$(H_{c})$과 보자력 분포도는 조성 이외의 제조공정인자에 크게 의존하는 값으로 자성분말 제조시 재현성을 결정하는 중요한 물성중의 하나이다. 자성분 말의 자기적 물성을 측정하는 VSM을 이용하여 쉽고 간단하게 보자력 분포도를 측정하는 방법과 그 응용예를 제시하였다. 보자력 분포도 측정은 magnetic hysteresis loop 의 dM/dH 대 H 곡선의 형태와 반치폭에서 얻을 수 있다. dM/dH 곡선 형태가 분리되는 것 없이 반치폭이 작아질수록 보자력 분포도는 더 균일해짐을 나타낸다. 보자력이 다 른 Ba-Ferrite와 ${\gamma}-Fe_{2}O_{3}$ 혼합물 중 Ba-Ferrite의 $H_{c}$가 높아질수록 dM/dH 대 H 곡선 형태는 peak broadening 후 peak splitting으로 나타나며, 이 peak splitting은 혼합자성분말의 $H_{c}$ 차이가 600 Oe 이상일 때 일어난다. 또한 dM/dH 대 H 곡선의 응용으로는 자성분말 보자력 분포도 측정, Ba-Ferrite 구조내로 dopants의 치환 능력 및 ${\alpha}-Fe$의 산화거동을 연구하는데 사용될 수 있다.

• 한국전기전자재료학회논문지
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• 제15권3호
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• pp.281-286
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• 2002

In odder to investigate the magnetic properties of CoCr-based bilayered thin films on kind of underlayer, we introduced amorphous Si layer to Co-Cr(-Ta) magnetic layer as underlayer. First, we prepared CoCr and CoCrTa single layer using the Facing Targets Sputtering system to investigate theirs properties. It was revealed that with increasing the film thickness of CoCr, CoCrTa single layer, crystalline orientation and perpendicular coercivity was improved. The CoCrTa thin film showed bettor crystalline and magnetic characteristics than CoCr thin film. As a result of investigating magnetic properties of CoCr and CoCrTa magnetic layer on introducing the Si underlayer, perpendicular coercivity and saturation magnetization of CoCr/Si and CoCrTa/Si bilayered thin film were decreased due to the increased grain size and diffusion of Si atoms to magnetic layer. And they showed constant with increasing the film thickness of Si thin film. However, in case of CoCrTa/Si bilayered thin film, in-plane coercivity was controlled low at about 250Oe. The c-axis orientations of CoCr/si and CoCrTa/Si bilayered thin film showed a good crystalline characteristics as about $2^{\circ}$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1988년도 추계학술대회 논문집
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• pp.46-46
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• 1988

Structural and magnetic properties of Co-Cr-Mo films were investigated in connection with sputtering conditions. Films were prepared using a convention RF sputtering system. X-ray diffractometry, scanning electron microscopy and transmission electron microscopy were employed to investigate structure properties. Vibrating sample magnetometry was used for coercivity and saturation magnetization measurements. Co-Cr-Mo films displayed reasonable values of perpendicular coercivity and saturation magnetization for perpendicular recording media and showed good perpendicular orientation of the hcp c-axis to the film surface. Perpendicular coercivity was strongly dependent upon substrate technique showed better c-axis orientation than hose using the stationary substrate. Co-Cr-Mo films of 2.9 at. % Mo content showed maximum perpendicular coercivity and saturation magnetization. The films deposited at lower Ar pressure showed good magnetic properties. There was no explicit relationship between the columnar structure and c-axis orientation. Co-Cr-Mo films was found to have suitable structural and magnetic properties for perpendicular recording media.

• 한국자기학회지
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• 제5권5호
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• pp.618-622
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• 1995

We studied the effects of Pt and Cr addition in a new Co-Cr-P-Pt alloy system with the coercivity higher than 2000 Oe even when they were deposited without substrate heating and bias voltage. The coercivity of the films increased from 1000 to 2000 Oe or higher by addition of 12 at.%Pt. The variation of the anisotropy field with increasing Pt content was similar to that of the coercivity. This indicate that the increase of the coercivity might be associated with increase of the anisotropy field with Pt addition. With the addition of Cr, the coercivity of the films increased up to 8 at.%Cr and the coercive squareness of the films decreased. The angular variation of coercivity deviated at a lower angle from domain wall motion mode as the Cr content increases. From these result, it is believed that the grain isolation of the films is enhanced with the addition of Cr.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1992년도 추계학술대회 논문집
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• pp.7-10
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• 1992

CoNiCr/Cr and CoCrTa/Cr for longitudinal magnetic recording media were. prepared on Coming 7059 glass by RF magnetron sputtering. The thickness of Cr underlayer was varied from 500 to $3000{\AA}$ and. that of magnetic layer was $700{\AA}$. Coercivity and squareness were measured using V.S.M.(vibrating sample magnetometer). The coercivity of films increased with increasing Cr thickness when the films were unannealed. The coercivity of the films annealed in a 10 mtorr vacuum increased initially with annealing time and then saturated with further increase in annealing time. The coercivity value difference between the unannealed and annealed films increased with increasing the thickness of Cr underlayer No significant change was found in squareness after anneal, regardless of Cr underlayer thickness.