• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2011년도 임시총회 및 하계학술연구발표회
• /
• pp.3-3
• /
• 2011

Since the first discovery of exchange anisotropy on Co/CoO system[1], there have been numerous studies to explore the physical origin of exchange-biased system[2,3]. In this presentation, we report that how the polarized neutron reflectomery can be applied to study the magnetization reversal behavior of the exchange biased system. As an example, the detailed magnetization reversal mechanism of the exchange-biased Py(30 nm)/FeMn (0, 15, 30 nm)/CoFe(30 nm) trilayers was studied and found that the 15 nm antiferromagnetic FeMn layer mediates the magnetization reversal behaviors of both Py and CoFe layers through interlayer exchange bias coupling. We also update the current activities in polarized neutron reflectometer in HANARO.

• Journal of Magnetics
• /
• 제11권2호
• /
• pp.61-65
• /
• 2006

The physical origin of complex dynamic domain configuration in nonequilibrium magnetic systems with mesoscopic length scales has been studied. An increasing complexity in the spatial feature of the evolution is found to accompany the increasing reversal speed, when a ferromagnetic element is driven by progressively faster switching fields applied antiparallel to the initial magnetization direction. As reversal rates approach the characteristic precession frequencies of spin fluctuations, the thermal energy can boost the magnetization into local configurations which are completely different from those experienced during quasistatic reversal. The sensitive dependence of the spatial pattern on switching speed can be understood in terms of a dynamic exchange interaction of thermally excited spins; the coherent modulation of the spins is strongly dependent on the rise time of switching pulses.

• Journal of Magnetics
• /
• 제16권2호
• /
• pp.97-100
• /
• 2011

Bilayers of soft NiFe (150 nm-420 nm) on hard Ni (150 nm) were prepared by electrodeposition. The process of magnetization reversal in the NiFe/Ni bilayers was then investigated. The hysteresis loop generated by a magnetization reversal of soft NiFe under a positive saturation state of a hard Ni layer shows a shift along the negative field axis, which is clear evidence for the exchange spring effect in the NiFe/Ni bilayers. The dependence of the coercive field $H_c$ and exchange bias field Hex on the thickness of the NiFe layer was also investigated. As the NiFe thickness increases from 150 nm to 420 nm, both $H_c$ and $H_{ex}$ decrease rapidly from $H_c$= 51.7 Oe and $H_{ex}$ = 12.2 Oe, and saturate to $H_c$ = 5.8 Oe and $H_{ex}$ = 3.5 Oe.

• 한국자기학회지
• /
• 제11권5호
• /
• pp.179-183
• /
• 2001

Glass/Ni$_{83}$Fe$_{17}$(2 nm)/[Cu(2 nm)Ni$_{83}$Fe$_{17}$(20 nm)]$_{50}$ 다층박막의 평면 홀 효과를 측정하였다. 평면 홀 효과에서 반복된 톱니모양의 홀 효과 신호가 관측되었다. 그 원인으로 갑작스러운 자벽의 이동이 홀 효과로 관측된 것이라는 가설을 세울 수 있다. 이러한 톱니모양의 평면 홀 효과는 모든 측정방향에서 관측되었다. 각 자성층의 전체 자화만이 자기저항을 결정하므로 자기저항의 특성곡선에서는 이러한 톱니모양에 해당하는 신호가 관측되지 않았다. 톱니모양의 근본 원인에 대한 연구는 더욱 수행되어야할 것이다.것이다.

• Journal of Magnetics
• /
• 제11권2호
• /
• pp.66-69
• /
• 2006

Local magnetization reversal in the exchange-biased NiFe/FeMn and $[Pd/Co]_5/FeMn$ multilayers with in-plane and out-of-plane magnetic anisotropy was achieved by using laser annealing. The local annealed NiFe/FeMn film under the opposite magnetic field shows a magnetoresistance (MR) curve having two symmetric peaks at the positive and negative exchange biasing field (${\pm}H_{ex}$). The intensity of the nucleated MR peak rises as the exposed area extends during the laser annealing process, and the peak disappears under the reverse magnetic field. In the case of [Pd/Co]/FeMn films, the local magnetization reversal increased gradually as the laser power increases. The locally reversed magnetization was restored under the opposite magnetic field.

• 한국자기학회지
• /
• 제6권4호
• /
• pp.199-203
• /
• 1996

Co/Pd 다층박막의 자화반전 거동을 조사하기 위하여, 먼저 시료를 자기장 소거법으로 탈자시킨 다음 초기자화 곡선과 minor loops 를 측정하였다. 또한 보자력 및 포화자화는 수직자화곡선으로부터 구하였으며, 수직자기이방성은 온도별로 측정한 수직 및 수평자화곡선의 면적차이를 이용하여 구하였다. 자화반저거동의 분석을 위하여 여러가지 정상적이고 반정량적인 방법을 측정결과에 적용하였다. 이들 결과로부터 본 실험에 사용된 시료의 자화반전의 지배적인 거동은 자벽의 pinning이며, 스퍼터링 압력이 증가할수록 보자력이 증가하는 경향은 Kronmuller 식 $H_{c}$ (T) .var. $r_{o}$ .center dot. $K_{u}$에 의해 설명될 수 있었다.다.다.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2002년도 동계연구발표회 논문개요집
• /
• pp.186-187
• /
• 2002

Recently, there has been much interest in magnetic thin film patterned in submicron scale because of possible ultrahigh density storage media or logical device applications [1-3]. Various geometries such as rectangle, circle, ring and ellipse type dots have been studied to find the shape showing stable switching behavior from repeated cycles. However, rectangle and circle types may not be suitable for device applications because they have two uncontrollable different magnetization reversal modes: C state and S state, resulting in different coercivity and irreproducible switching[4]. (omitted)

• 한국자기학회지
• /
• 제5권4호
• /
• pp.261-268
• /
• 1995

비대칭 자화 반전 효과의 원인을 조사하기 위하여 ${(Fe_{1-x}Co_{x})}_{75}Si_{10}B_{15}$계 비정질 자성 합금 리본을 부자장 중에서 열처리 온도 $380^{\circ}C$로 하여 16시간 동안 열처리한 후 합금 조성에 따른 자기 이력 곡선의 변화에 대하여 연구하였다. Fe나 Co만을 함유하고 있는 하금의 경우보다 이들 두 금속을 모두 함유하고 있는 비정질 합금 리본의 경우가 무자장 열처리에 의해서 자구벽내에 더 큰 유도 자기 이방성을 형성함으로써 보다 뚜렷한 비대칭 자화 반전 효과를 얻을 수 있었다. 또한 영자왜 조성에 가까운 비정질 합금의 경우에서 보다 뚜렷한 비대칭 자화 반전 효과를 얻을 수 있었는데, 두가지 금속 모두를 함유하는 특히 서로 비슷한 함량을 함유 하는 조성을 가질수록 뚜렷한 효과를 얻을 수 있다는 사실과 복합적으로 적용하였다.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2000년도 International Symposium on Magnetics The 2000 Fall Conference
• /
• pp.287-296
• /
• 2000

We have developed a three-axis configurational in situ SMOKE apparatus by which three-dimensional vector magnetization reversal processes are studied for ultrathin Co films grown on a Pd (111) single crystal in the thickness range of spin-reorientation transition. This study provides a better understanding of magnetization reversal motions with the knowledge of 3 components of magnetization vector at the transition of an easy axis of magnetization from the film normal at 5 ML Co to in-plane at 6 ML Co (ML notes monolayer). For a 5.25 ML Co, it was observed that a slightly canted magnetization vector from the film normal rotated in the film plane under an applied field direction parallel to the film normal.

• Journal of Magnetics
• /
• 제6권2호
• /
• pp.53-56
• /
• 2001

We have developed a three-axis configurational in situ SMOKE apparatus by which three-dimensional vector magnetization reversal processes are studied for ultrathin Co films grown on a Pd (111) single crystal in the thickness range of spin reorientation transition. This study provides a better understanding of magnetization reversal motions with the knowledge of three components of the magnetization vector at the transition of an easy axis of magnetization from the film normal at 5 ML Co to in-plane at 6 ML Co (ML denotes monolayer). For a 5.25 ML Co, it was observed that a slightly canted magnetization vector from the film normal rotated in the film plane under an applied field direction parallel to the film normal.