• Journal of the Korean Ceramic Society
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• v.28 no.8
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• pp.603-610
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• 1991

An oxygen deficient perovskite (CaLa)(MgMn)O5.43, with the cubic unit cell parameter of 3.826$\AA$, was prepared 115$0^{\circ}C$ for 10 hrs under the ambient oxygen gas pressure. The average oxidation state of manganese was determined to be 3.86 by the iodometric titration, so that the perovskite could be formulated as (CaLa) ({{{{ { MgMn}`_{ chi } ^{II } }}{{{{ { Mn}`_{ y} ^{III } }}{{{{ { Mn}`_{1- chi -y } ^{IV } }})O5.43 (2x+y=0.14). From X-ray photoelectron spectroscopy, the manganese ions in the lattice are mostly tetravalent, but two paramagnetic configurations were observed in the EPR spectrum: One sharp isotropic signal with hyperfines (ΔH 50 G, g=1.997$\pm$0.002 and │A│=82(4)$\times$10-4 cm-1) and a broad isotropic one (ΔH 1600 G, g=1.994$\pm$0.002), those which correspond respectively to Mn(II) and Mn(IV) ions. According to the magnetic susceptibility measurement, it follows the Curie-Weiss law from 20 K up to room temperature with $\mu$eff=5.23 $\mu$B, which is relatively larger than spin-only value({{{{ { mu }`_{eff} ^{s.o } }}=4.04 $\mu$B) due to the effect of weak ferromagnetic coupling. Such a result is in accord with a theory of semicovalence exchange.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.156-159
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• 2003

The stochiometric mixture of evaporating materials for the $CuInTe_2$ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, $CuInTe_2$ mixed crystal was deposited on throughly etched GaAs(100) by the Hot Wall Epitaxy(HWE) system. The source and substrate temperature were $610^{\circ}C\;and\;450^{\circ}C$ respectively, and the growth rate of the single crystal thin films was about $0.5{\mu}m/h$. The crystalline structure of single crystal thin films was investigated by the double crystal X-ray diffraction(DCXD). From the photocurrent spectra, we have found that values of spin orbit coupling ${\Delta}So$ and crystal field splitting ${\Delta}Cr$ ware $0.283{\underline{3}}eV\;and\;0.120{\underline{0}}eV$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.134-135
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• 2006

$AgInS_2$ single crystal thin filmsl was deposited on throughly etched semi-insulator GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $680^{\circ}C$ and $410^{\circ}C$ respectively, and the thickness of the single crystal thin films is $6{\mu}m$. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $AgInS_2$ single crystal thin film, we have found that the values of spin orbit coupling ${\Delta}So$ and the crystal field splitting ${\Delta}Cr$ were 0.0098 eV and 0.15 eV at 10 K, respectively. In order to explore the applicability as a photoconductive cell, we measured the sensitivity ($\gamma$), the ratio of photocurrent to darkcurrent (pc/dc), maximum allowable power dissipation (MAPD), spectral response and response time. The result indicated that the samples annealed in S vapour the photoconductive characteristics are best. Therefore we obtained the sensitivity of 0.98, the value of pc/dc of $1.02{\times}10^6$, the MAPD of 312 mW, and the rise and decay time of 10.4ms and 10.8ms respectively.

• Journal of Magnetics
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• v.5 no.1
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• pp.23-25
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• 2000

We have investigated the effects of Ar and$O_2$-ion milling on the exchange coupling field ($H_{ex}$) and coercive field ($H_c$) at the interfaces between substrates and NiO/NiFe films, to understand the exchange biasing mechanism. The $O_2$-ion milling was successfully performed by means of the electron cyclotron resonance (ECR) process. We found that the local roughness gradient of the NiO surface increased by $O_2$-ion milling. The ratio of $H_{ex}/H_c$ increased from 0.87 to 1.77, whereas $H_c$ decreased by almost a half as a results of the ion milling. The decrease in $H_c$could be interpreted as due to the refinement of magnetic domain size, which arose from the increase of the local roughness gradient of the NiO surface. The decrease in low $H_c$, and increase in $H_{ex}$ in NiO spin valves by ECR-ion milling are in the right direction far use in magnetoresistance (MR) heads.

• Journal of the Korean Magnetics Society
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• v.18 no.5
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• pp.180-184
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• 2008

The relation of ferromagnet anisotropic magnetization and the antiferromagnet atomic spin configuration has been investigated for variously angles of unidirectional deposition magnetic field of FeMn layer in Corning glas/Ta(5 nm)/NiFe(7 nm)/FeMn(25 nm)/ Ta(5 nm) multilayer prepared by ion beam deposition. Three unidirectional deposition angles of FeMn layer are $0^{\circ},\;45^{\circ}$, and $90^{\circ}$, respectively. The exchange bias field ($H_{ex}$) obtained from the measuring easy axis MR loop was decreased to 40 Oe in deposition angle of $45^{\circ}$, and to 0 Oe in the angle of $90^{\circ}$. One other side hand, $H_{ex}$ obtained from the measuring hard axis MR loop was increased to 35 Oe in deposition angle of $45^{\circ}$, and to 79 Oe in the angle of $90^{\circ}$. Although the difference of uniderectional axis between ferromagnet NiFe and antiferromagnet FeMn was 90o, the strong antiferromagnetic dipole moment of FeMn caused to rotate the weak ferromagnetic dipole moment of NiFe in the interface. This result implies that one of origins for exchange coupling mechanism depends on the effect of magnetic field angle during deposition of antiferromgnet FeMn layer.

• Journal of the Korean Magnetics Society
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• v.27 no.4
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• pp.123-128
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• 2017

The magnetic isotropy property from the magnetoresistance (MR) curve and magnetization (MH) loop for the PtMn based spin valve (SV) multilayer films fabricated with different the bottom structure after post-annealing treatment was investigated. The exchange biased coupling field ($H_{ex}$), coercivity ($H_c$), and MR ratio of Glass/Ta(10 nm)/CoFe(6 nm)/Cu(2.5 nm)/CoFe(3 nm)/Ta(4 nm) SV multilayer film without antiferromagnetic PtMn layer are 0 Oe, 25 Oe, and 3.3 %, respectively. MR curve for the Glass/Ta(10 nm)/CoFe(6 nm)/Cu(2.5 nm)/CoFe(3 nm)/PtMn(6 nm)/Ta(4 nm) SV multilayer film showed $H_{ex}=2Oe$, $H_c=316Oe$, and MR (%) = 4.4 % with one butterfly MR curve having by the effect of antiferromagnetic PtMn layer. MR curve for the dualtype Glass/Ta(10 nm)/CoFe(6 nm)/Cu(2.5 nm)/CoFe(3 nm)/PtMn(6 nm)/CoFe(3 nm)/Cu(2.5 nm)/CoFe(6 nm)/Ta(4 nm) SV multilayer film showed $H_c=37.5Oe$ and 386 Oe, MR = 3.5 % and 6.5 % with two butterfly MR curves and square-like hysteresis MH loops. The anisotropy property in CoFe spin valve-PtMn multilayer is neglected by the effects of a very small value of $H_{ex}$ and a very slightly shape magnetic anisotropy. This result is possible to explain the effect of magnetization configuration spin array of the bottom SV film and the top SV film of PtMn layer.

• Journal of the Korean Magnetics Society
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• v.19 no.2
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• pp.52-56
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• 2009

Interlayer coupling field, coercivity, magnetoresitance ratio, and magnetic sensitivity depending on the thickness of free CoFe layer for the CoFe/Cu/CoFe/IrMn multilayer are investigated. In case of CoFe layer of $30\;{\AA}$ thickness for the CoFe(t)/Cu($25\;{\AA}$)/CoFe($60\;{\AA}$)/IrMn($80\;{\AA}$) multilayer with ferromagnet/non-magnet/ferromagnet structure induced by IrMn layer, the lowest coercivity and the highest magnetic sensitivity, which is contained soft magnetic property, are observed. On the other side, in case of CoFe layer of $90\;{\AA}$ thickness, there are the highest coercivity and the lowest magnetic sensitivity. The fabricated CoFe($30\;{\AA}$)/Cu($25\;{\AA}$)/CoFe($60\;{\AA}$)]/IrMn($80\;{\AA}$) spin valve device with $2{\times}8{\mu}m^2$ patterning size are measured by two probe method, which is selected the sensing current as the longitudinal direction and the easy axis as the transversal direction. The measuring magntoresistance ratio and magnetic sensitivity of GMR-SV device having the soft magnetic property are 3.0% and 0.3%/Oe, respectively.

• Polymer(Korea)
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• v.24 no.3
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• pp.389-398
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• 2000

Transparent, abrasion resistant coatings with 4~13 ${\mu}{\textrm}{m}$ thickness were prepared by spin-coating on polycarbonates with organic/inorganic hybrid solutions, followed by UV curing and heat treatment at 12$0^{\circ}C$ for 12 hours. The coating solutions were composed of inorganic phase and organic phase in 0:100, 20:80, 30:70, 50:50, 80:20 wt% ratios, respectively, mixed with photoinitiator, senaitizer and surfactant. The inorganic phase was formed by sol-gel reaction of TEOS and silane coupling agent MPTMS in 1 : 2 or 2 : 1 molar ratios, the organic phase consisted of difunctional urethane acrylate oligomeric resin, multifunctional acrylate TMPTA and HDDA in 4 : 3 : 3 wt% ratio. The coating systems were investigated by FT-IR, $^{29}$ Si-NMR spectra. In addition, TGA/DSC for thermal analysis and SEM, AFM observation for coated surface were examined. Gererally, the homogeneity of phases, the surface smoothness of coating and abrasion resistance were improved with the higher content of inorganic component. Namely, coating system with below 10 $\AA$ surface roughness and T$_{g}$ of 15$0^{\circ}C$ showed only 10% decrease in light transmittance after abrasion test, whereas uncoated polycarbonate substrate exhibited 46% decrease..

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.14-15
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• 2010

Recently there has been growing interest in topological insulators or the quantum spin Hall (QSH) phase, which are insulating materials with bulk band gaps but have metallic edge states that are formed topologically and robust against any non-magnetic impurity [1]. In a three-dimensional material, the two-dimensional surface states correspond to the edge states (topological metal) and their intriguing nature in terms of electronic and spin structures have been experimentally observed in bulk Bi1-xSbx single crystals [2,3,4]. However, if we want to know the transport properties of these topological metals, high purity samples as well as very low temperature will be needed because of the contribution from bulk states or impurity effects. In a recent report, it was also shown that an intriguing coupling between the surface and bulk states will occur [5]. A simple solution to this bothersome problem is to prepare a topological metal on an ultrathin film, in which the surface-to-bulk ratio is drastically increased. Therefore in the present study, we have investigated if there is a method to make an ultrathin Bi1-xSbx film on a semiconductor substrate. From reflection high-energy electron diffraction observation, it was found that single crystal Bi1-xSbx films (0${\sim}30\;{\AA}A$ can be prepared on Si(111)-$7{\times}7$. The transport properties of such films were characterized by in situ monolithic micro four-point probes [6]. The temperature dependence of the resistivity for the x=0.1 samples was insulating when the film thickness was $240\;{\AA}A$. However, it became metallic as the thickness was reduced down to $30\;{\AA}A$, indicating surface-state dominant electrical conduction. Figure 1 shows the Fermi surface of $40\;{\AA}A$ thick Bi0.92Sb0.08 (a) and Bi0.84Sb0.16 (b) films mapped by angle-resolved photoemission spectroscopy. The basic features of the electronic structure of these surface states were shown to be the same as those found on bulk surfaces, meaning that topological metals can be prepared at the surface of an ultrathin film. The details will be given in the presentation.

• Journal of the Korean Magnetics Society
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• v.13 no.3
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• pp.97-102
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• 2003

Synthetic ferrimagnetic layer (SyFL) with structure NiFe/Ru/NiFe which can be applied high density TMR device in free layer were prepared by an inductively coupled plasma (ICP) helicon-sputter. We proposed a model of predicting coercivity (H$\_$c/), spin-flopping field (H$\_$sf/), and saturation field (H$\_$s/) as a function of Ru thicknesses, from the equilibrium state of energies of Zeeman, exchange, and uniaxial anisotropy. We fabricated the samples of Ta(50 ${\AA}$)/NiFe(50${\AA}$)nu(4∼20${\AA}$)NiFe(30 ${\AA}$)/Ta(50${\AA}$), and measured the M-H loops with a superconduction quantum interference device (SQUID) applying the external field up to ${\pm}$ 15 kOe. The result was well agreed with the proposed model, and reveal K$\_$u = 1000 erg/㎤, J$\_$ex/ =0.7 erg/$\textrm{cm}^2$. We report that H$\_$c/ below 10 Oe is available, and R$\_$u/ thickness range should be in 4-10 ${\AA}$ for MRAM application. Our result implies that permalloy layers may lead to considerable magnetostriction effect in SyFL and intermixing in NiFe/Ru interfaces.