• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.570-574
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• 1995

Magnetoresistance of NiFeCo/Cu/NiFeCo/FeMn uncoupled exchange biased sandwiches has been studied. The magnetoresistance change ratio, ${\Delta}R/R_{s}$ showed 4.1 % at a saturation field as low as 11 Oe in $Si/Ti(50\;{\AA})/NiFeCo(70\;{\AA})/Cu(23\;{\AA})/NiFeCo(70\;{\AA})/FeMn(150\;{\AA})/Cu(50\;{\AA})$ spin valve structure. In this system, the magnetoresistance was affected by interlayer material and thickness. When Ti and Cu were used as the interlayer material in this structure, maximum magnetoresistance change ratio were 0.32 % and 4.1 %, respectively. 6.1 % MR ratio was obtained in $Si/Ti(50\;{\AA})/NiFeCo(70\;{\AA})/Cu(15\;{\AA})/NiFeCo(70\;{\AA})/FeMn(150\;{\AA})/Cu(50\;{\AA})$ spin valve structure. The magnetoresistance change ratio decreased monotonically as the interlayer thickness increased. It was found that the exchange bias field exerted by FeMn layer to the adjacent NiFeCo layer was ~25 Oe, far smaller than that reported in NiFe/Cu/NiFe/FeMn spin valve structure(Dieny et. al., ~400 Oe). The relationship between the film texture and exchange anisotropy ha been examined for spin valve structures with Ti, Cu, or non-buffer layer.

• Journal of the Korean Magnetics Society
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• v.6 no.3
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• pp.189-193
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• 1996

Magnetoresistance field sensitivity and magnetostriction were measured as a function of annealing temperature for NiFe/Ag multilayer systems displaying giant magnetoresistance. Key multilayer configurations such as number of NiFe/Ag bilayers and Ag spacer thickness were varied. A high giant magnetoresistance ratio up to 5% with zero magnetostriction and high magnetoresistance field sensitivity was possible to achieve simultaneously with optimal sample geometry and annealing condition.

• Journal of Magnetics
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• v.6 no.3
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• pp.83-85
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• 2001

The magnetoresistance properties of NiO/NiFe/Cu/NiFe spin valve film deposited on MgO(100) substrate with YBa$_2$$Cu_3O_7$(YBCO) film were investigated at room temperature and at 77 K. The magnetoresistance (MR) curves of the hybrid superconductor-magnetoresistor film structure showed an exchange coupling field of 300 Oe and an inverse magnetoresistance ratio of -6.5%. The magnetization configurations of the two magnetic layers in the NiO spin valve were antiparallel due to an increment in the conduction electron flow to superconductor YBCO film. This sample showed an inverse MR ratio.

• Journal of Magnetics
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• v.7 no.3
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• pp.98-100
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• 2002

Tunnel magnetoresistive devices using an individual multi-walled carbon nanotube were fabricated and their low-temperature electrical transport propertiers were investigated. With the ferromagnetic Co electrodes, the multi-walled carbon nanotube exhibited hysteretic magnetoresistance curve at low temperatures. Depending on the temperature and the bias current, the magnetoresistance ratio can be as high as 16% at the temperature of 2.2 K. Such high magnetoresistance ratio indicates a long diffusion length of the multi-walled carbon nanotube.

• Electrical & Electronic Materials
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• v.10 no.10
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• pp.1016-1021
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• 1997

Magneto resistance properties in spin-valve sandwiches with various thickness of nanmagnetic layer in contact with the ferromagnetic NiFe film were investigated. The NiFe layer in contact with the NiO film was pinned by strongly exchange-biased coupling and the free NiFe layer at the film surface induced a sharp change in the magnetoresistance at -5~15Oe due to small coercivity. The NiO/NiFe/Cu/NiFe film showed a magnetoresistance ratio in the range of 2.3~2.9% and a field sensitivity above 2.2%/Oe with various of nonmagnetic layer. The NiO/NiFe/Cu/NiFe film of the field sensitivity above 2.2%/Oe suggests stang possibility of magnetic sensor matter.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.451-455
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• 1995

The composition and thickness dependence and the ferromagnetic under- and overlayer effect on the magnetoresistance ratio and saturation field of the Co-Ag nano-granular films were investigated. The maximum magnetoresistance (23% at R.T.) in the as-deposited state was obtained in the $3000{\AA}$ $Co_{30} Ag_{70}$ bare alloy film. As the thickness of the alloy films decreased below $500{\AA}$, the MR ratio decreased because of the resistivity increase and the non-uniform film formation. We showed that the ferromagnetic over- and underlayer could reduce the saturation field of the nano-granular films via exchange coupling effect. The magnetoresistance and the saturation field of the $100{\AA}$ alloy film were 3.65 % and 2.85 kOe respectively and those of the under- and overlayered alloy films with $200{\AA}$ Fe were 3.3 % and 1.23 kOe respectively.

• Journal of the Korean institute of surface engineering
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• v.32 no.1
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• pp.61-66
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• 1999

The Spin-dependent tunneling magnetoresistance (TMR) effect was observed in $NiFe/Al_2O_3$/Co thin films. The samples were prepared by magnetron sputtering in a system with a base pressure of $3\times10^{-6}$Torr. the insulating $Al_2O_3$layer was prepared by r.f. plasma oxydation method of a metallic Al layer. The ferromagnetic and insulating layers were deposited through metallic masks to produce the cross pattern form. The junction has an active area of $0.3\times0.3\textrm{mm}^2$ and the $Al_2O_3$layer is deposited through a circular mask with a diameter of 1mm. It is very important that insulating layer is formed very thinly and uniformly in tunneling junction. The ferromagnetic layer was fabricated in optimum conditions and the surface of that was very flat, which was observed by AFM. Tunneling junction was confirmed through nonlinear I-V curve. $NiFe/Al_2O_3$/Co junction was observed for magnetization behavior and magnetoresistance property and magnetoresistance property is dependent on magnetization behavior and magnetoresistance property and magnetoresistance property is dependent on magnetization behavior of t재 ferromagnetic layer. The maximum magnetoresistance ratio was about 6.5%.

• Journal of the Korean Magnetics Society
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• v.8 no.5
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• pp.282-287
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• 1998

Dependence of magnetoresistance on base pressure and deposition rates of each Fe, Co, Cu layers in the $Fe(50{\AA}/[Co(17{\AA})/Cu(24{\AA})]_20$ multilayer thin films, prepared by dc magnetron sputtering on Corning glass, were investigated. AFM analysis, X-ray diffraction analysis, vibrating sample magnetometer analysis, and magnetoresustance measurement (4-probe method) were performed. The multilayer films deposited under low base pressure increases magnetoresistance ratio by preventing oxidation. Annealing for the samples at a moderate temperature allowed larger textured grain with no loss in the periodicity. Magnetoresistance ratio of the annealed multilayers was increased due to the increase antiferromagnetically coupled fraction of the film after annealing. Optimization of deposition rate was greater than 1 $\AA$/s for Fe, and 2.8 $\AA$/s for Cu. Deposition rate of Co showed a tendency of increasing of magnetoresistance ratio due to the formation of flat magnetic layer in case of high deposition rate of Co.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.5
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• pp.811-816
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• 2006

The single layered magnetic thin films with anisotropic magnetoresistance behavior have advantage on micro integration due to their low cost in manufacturing. Although the conventional MCo (M=Cu, Ag) amorphous ribbons using a rapid solidification process have showed appropriate for magnetic property for bulk devices, they are not appropriate for micro-scale devices due to their brittleness. We prepared the thermal evaporated 100 nm-thick $Cu_{1-x}Co_x\;and\;Ag_{1-x}Co_x(x=0.1{\sim}0.7)$ films on silicon wafers and investigated the magnetic property of the as-depo films such as magnetization and magnetoresistance ratio. We confirmed that the maximum MR ratio of 1.4 and 2.6% at the external field of 0.5 Tesla in $CuCo_{30},\;AgCo_{40}$ films, respectively. Our result implies that AMR may be slightly less than those of the conventional CuCo and AgCo ribbons due to surface scattering, but their AMR ratio be enough for micro-scale application with easy integration compatibility for the process without surface oxidation.

• Electrical & Electronic Materials
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• v.9 no.10
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• pp.1060-1065
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• 1996

We have studied the magnetoresistance phenomena on spin valve thin films of antiferromagnetic NiO/CoO. Interlayer coupling oscillates between the antiferrocoupling and ferrocoupling with the variation of Cu thickness. The exchange coupling strength between NiO (antiferromagnetic) and NiFe(ferromagnetic) as a function of NiO texture and interface roughness is investigated by CoO insertion. CoO has significantly higher anisotropy in the (111) plane and interface roughness. It seems that the MR-ratio is increased by CoO inserted films. From the AFM and XRD data, the increase of MR-ratio and exchange field is influenced by the roughness of CoO.