• Electrical & Electronic Materials
• /
• v.14 no.5
• /
• pp.3-8
• /
• 2001

• Journal of the Korean Magnetics Society
• /
• v.13 no.6
• /
• pp.243-245
• /
• 2003

The anomalous angular modulation of magnetoresistance in Co/Cu multilayers is explained assuming substrate-induced magnetic anisotropy. The magnetic parameters of Co/Cu multilayers is determined using angular modulation of magnetoresistance and theoretical model including substrate-induced anisotropy. This mechanism introduces a new possible way of modulating the giant magnetoresistance.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2002.12a
• /
• pp.102-103
• /
• 2002

LaMnO$_3$에 Ca을 치환한 Mn계 perovskite 구조(ABO3)의 물질에서 초거대자기저항 현상이 발견된 이후 R$_{1-x}$$^{3+}$ A$_{x}$$^{2+}$MnO$_3$(R=La, Nd, Pr: 희토류금속, A=Ca, Sr, Ba, Cd, Pb; 2가 양이온)계의 Mn 산화물의 연구가 고감도 자기 저항 센서와 자기기록 등의 활용가능성을 중심으로 활발히 진행되고 있다. 자기적 특성이 뛰어난 초거대자기저항물질에 대한 미시적인 자성에 대한 연구는 그 메커니즘이 복잡하고 다양한 접근방식에 따른다. (중략)

• Journal of the Korean Magnetics Society
• /
• v.9 no.6
• /
• pp.301-305
• /
• 1999

NiFe(60$\AA$)/Co(5$\AA$)/Cu(60$\AA$)/Co(30$\AA$) spin valve thin films were patterned into magnetoresistive random access memory (MRAM) cells by a conventional optical lithography process and their output and switching properties were characterized with respect to the cell size and geometry. When 1 mA of constant sense current was applied to the cells, a few or a few tens of mV of output voltage was measured within about 30 Oe of external magnetic field, which is an adequate output property for the commercializing of competitive MRAM devices. In order to resolve the problem of increase in the switching thresholds of magnetic layers with the downsizing of MRAM cells, a new approach using the controlled shape anisotropy was suggested and interpreted by a simple calculation of anisotropy energies of magnetic layers consisting of the cells. This concept gave a reduced switching threshold in NiFe(60$\AA$)/Co(5$\AA$) layer consisting of the patterned cells from about 15 Oe to 5 Oe and it was thought that this concept would be much helpful for the realization of competitive MRAM devices.

• Journal of the Korean Magnetics Society
• /
• v.8 no.4
• /
• pp.231-240
• /
• 1998

We investigated that the fabrication and reproducing signal characteristics of tri-layered magnetoresistance (MR) element for the high density magnetic thin film heads and sensors. Magnetoresistance curve of tri-layered MR element predicted by computer modeling was saturated above external field of -15 Oe~+22 Oe, and it was shifted to linearized region as large as 4 Oe. In the case of fabricated real device, magnetoresistance curve was saturated above external field of $\pm$15 Oe, and it was shifted to linearized region as large as 4 Oe. As shown in real device, MR response curve was in good agreement with the simulation results. As a result of experimental data of reproducing output signal in real device, it retained normal sinusoidal waveforms in 1~4 Oe external magnetic field. In this magnetic field region, the fabricated heads with tri-layered MR element can be operated with good reproduced characteristics. This will be beneficial to the use of efficient processes of manufacturing elements and the vacuum deposition techniques which control thin film properties.

• Journal of the Korean Magnetics Society
• /
• v.12 no.6
• /
• pp.212-217
• /
• 2002

The pseudo spin valve with a structure of Tl/CoFe(t $\AA$)/Cu(30 $\AA$)/NiFe(50 $\AA$)/Ta, showing giant magnetoresistance properties by utilizing coercivity difference between only two soft ferromagnetic layers were produced by d.c UHV magnetron sputtering system. In pseudo spin valve Ta/CoFe/Cu/NiFe/Ta, the magnetic and magnetoresistance properties with change of CoFe thickness were investigated. When the thickness of CoFe was 60 $\AA$, a typical MR curve of pseudo spin valve structure was obtained, showing MR ratio of 3.8 cio and the coercivity difference of 27.4 Oe with a sharp change of hard layer switching. When the CoFe thickness was varied from 20 to 100 $\AA$, coercivity difference between two layers was increased to 40 $\AA$. and decreased to 100 $\AA$ gradually. It is thought the change in coercivity of hard layer was due to the crystallinity and magnetostriction of thin CoFe layer. In order to improve the MR property in CoFe/Cu/NiFe trier layer structure, CoFe layer with change of 2-20 $\AA$ thick was inserted between Cu and NiFe. When the thickness of CoFe was 10 $\AA$, MR ratio was 6.7％, showing excellent MR property. This indicates 50 ％ higher than that of CoFe/Cu/NiFe pseudo spin valve.

• Journal of the Korean Magnetics Society
• /
• v.9 no.5
• /
• pp.239-244
• /
• 1999

Bi-doped lanthanum magnetics $(La_{0.67-x}Bi_xCa_{0.33}MnO_3(x\;=\;0,\; 0.04,\; 0.1,\; 0.2))$ samples have been prepared by standard ceramic process. The crystallinity and microstructures of the samples have been investigated by x-ray diffractometry and optical microscopy, respectively. The magnetic and magnetoresistive properties of the samples have been measured by vibrating sample magnetometery and van der Pauw method, respectively, at the temperatures ranging of 100 K~300 K with applied magnetic field of 0.4~0.5 T. Good crystallinity and high Curie temperature (275 K) have been obtained for the Bi-doped samples with small dosage (x = 0.04, 0.1) even they were sintered at 120$0^{\circ}C$, which is about 20$0^{\circ}C$ lower than normal sintering temperature of 140$0^{\circ}C$. The Bi-doped samples with the small dosage showed lower relative electrical resistivity and higher magneto-resistive ratio compared to the undoped sample in the most temperatures measured. The Bi-doped samples also exhibited large magnetoresisitve ratio (maximum of 15% for x = 0.1) at room temperature even under a weak magnetic field of 0.4 T.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.23 no.4
• /
• pp.322-327
• /
• 2003

Giant magnetoresistance(GMR) NiO multilayer, which has been used to reading head of highly dense magnetic recording, was fabricated, and oxidized in an air during 80 days to study the dependence of magnetoresistance properties on residual stress in the interfaces. The magnetoresistance ratio and the exchange biasing $field(H_{ex})$ of $NiO(60nm)/Ni_{81}Fe_{19}(5nm)/Co(0.7nm)/Cu(2nm)/Co(0.7nm)/Ni_{81}Fe_{19}(7nm)$ spin valves were increased from 4.9% to 7.3%, and 110 Oe to 170 Oe after natural oxidation in the atmosphere for 80 days, respectively. The sheet resistivity ${\rho}$ decreased from $28{\mu}{\Omega}m$ to $17{\mu}{\Omega}m$, but ${\Delta}p$ did not almost change after the oxidation. Therefore, the increase of MR ratio is due to the decrease in the sheet resistivity. the reduced resistance may result from the increase in the reflection of conduction electrons at the oxidized top surface. Also, the increase in the exchange biasing field is originated from the reduction of residual stress at the interface of $NiO/Ni_{81}Fe_{19}$ according as the aging time increases.

• Journal of Sensor Science and Technology
• /
• v.3 no.1
• /
• pp.68-77
• /
• 1994

Grid type 70Ni-30Co thin films on slide glass at $250^{\circ}C$ has been fabricated to develope. From fabricated sensors using above process, we investigated the relation of temperature, resistivity, line width to magnetoresistance and we obtained the following results after observation of coercive force, saturated magnetization, maxium usable sensitivity, delay time, slew rate, white noise, resolution of the sensors. We confirmed that the $600{\AA}$ thin film at $250^{\circ}C$ formed crystalized magnetic anisotropy spontaneously and the sensor using the thin film had capability of detecting magnetic field with sensitivity of 230 nT. In these devices, the magnetoresistance change was increased linearly in ${\pm}10$ Oe range, and the magnetoresistance effect was increased when the ratio between line width and length was increased. When the devices was soldered using indium, the temperature-resistivity coefficient showed $8{\times}10^{-3}/deg$ and increased during the specific properties as magnetic field sensor were weakened. In this studies, the coercive forces of the films were about 5.1 A/cm and saturated magnetizations were 0.64 T, and the delay time in these devises was $5{\mu}s$ and slew rate showed 0.39 $Oe/{\mu}s$ and white noise was -120 dB.

• Journal of the Korean Magnetics Society
• /
• v.17 no.2
• /
• pp.95-98
• /
• 2007

In this paper, the magnetic properties and the annealing behavior of spin valve structures with Mo(MoN) underlayers were studied for various underlayer thickness. The spin valve structure was Si substrate/Mo(MoN)$(t{\AA})/NiFe(21{\AA})/CoFe(28{\AA})/Cu(22{\AA})/CoFe(18{\AA})/IrMn(65{\AA})/Ta(25 {\AA})$. Mo and MoN films were deposited on Si substrates and their thermal annealing behavior was analyzed. The deposition rate of the MoN thin film was decreased and tile resistivity of the MoN thin films were increased as the $N_2$ gas flow was increased. The variations of MR ratio and magnetic exchange coupling field of spin valve structure were smaller with MoN underlayers than that with Mo underlayers up to thickness of $51{\AA}$. MR ratio of spin valves with Mo underlayers was 2.86% at room temperature and increased up to 2.91 % after annealing at $200^{\circ}C$. Upon annealing at $300^{\circ}C$, the MR ratio decreased about 2.16%. The MR ratio of spin valves structure with MoN underlayers for $N_2$ gas flow 1 sccm was 5.27% at room temperature and increased up to 5.56% after annealing at $200^{\circ}C$. Upon annealing at $300^{\circ}C$, the MR ratio decreased about 4.9%.