• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.702-709
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• 1995

In this paper we review recent work in our laboratory on nanocomposite CoSm-based films including CoSm with Cr underlayer (CoSm//Cr), exchange-coupled magnetic films consisting of CoSm and FeCo layers (CoSm/FeCo), and CoSm multilayers with nonmagnetic spacing layers of SmO (CoSm/SmO). The emphasis is on detailed investigations of microstructure and magnetic properties for CoSm//Cr films, exchange-spring effects for CoSm/FeCo films, and interlayer effects for (CoSm/ SmO) multilayers.

• Journal of the Korean Magnetics Society
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• v.9 no.6
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• pp.312-320
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• 1999

Effect of deposition conditions on the magnetic properties of SmCo/Cr prepared by a RF magnetron sputtering method was studied. We obtained the maximum coercivity of 3.2 kOe in the sample of Cr(50 nm)/SmCo(40 nm, 50W, 20 mT)/Cr(150 nm, 100 W, 30 mT). The coercivity of the SmCo/Cr depends largely on the roughness of the Cr underlayer and the composition of SmCo. The roughness of the Cr underlayer increased with increasing the Ar pressure and thickness, and promoted the isolation of SmCo grains which resulted in an enhanced coercivity. The composition of the SmCo was changed with RF power and Ar pressure due to the mass difference between Sm and Co and the resputtering phenomena. The maximum coercivity was obtained in the composition of about 20 at.% Sm. The mechanism of magnetization reversal of the present SmCo films changed from domain wall motion to domain rotation as the RF power and the Ar pressure increase. This was though to be due to the defects, such as the roughness of Cr surface, porous column boundaries etc., which inhibit domain wall movement.

• Journal of the Korean Magnetics Society
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• v.13 no.5
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• pp.198-203
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• 2003

To investigate whether the use of hard magnetic film is available to generate bias magnetic field for a magnetoimpedance sensor, the magnetic properties of SmCo hard magnetic films were investigated as a function of their compositions. The saturation magnetization decreased with Sm content increasing in SmCo films. And, the coercive force increased in the extent of Sm content of 28 at%, but decreased as Sm content increased moreover. The bias field effect of SmCo film to amorphous CoZrNb film was investigated with the magnetization corves, permeabilities, and magnetic domain structures of SmCo/CoZrNb multilayers. The bias field of about 60 Oe was observed in the film with 3 mm ${\times}$ 0.5 mm, which can be constructed as a MI sensor, and this result strongly indicates that the bias field generated from a hard magnetic film is adequate to enhance the sensitivity of a MI sensor with hard/soft magnetic multilayer structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.12
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• pp.988-995
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• 2010

In this study the (Alnico, Sm-Co) bonded magnets were fabricated by mixing the Sm-Co added alnico alloy powders with epoxy resin and binder, appropriately. Also, the hybrid ring magnets of (Alnico, Sm-Co)/Sr-ferrite were fabricated by coupling the Sr-ferrite composite layer with an (Alnico, Sm-Co) magnet. The magnetic properties of (Alnico, Sm-Co) ring magnets were varied with the amount of Sm-Co powders. The addition of Sm-Co powders increased a remanent induction($B_r$) and coercive force($_BH_C$), while decreasing a surface flux density and repulsive distance. The surface flux density and repulsive distance for the (Alnico, Sm-Co) ring magnet increased with a magnetizing voltage up to about 160 V and reached an apparent saturation point. Also, the measurements of temperature and moisture characteristics showed that the surface flux densities of N-S poles and repulsive distance decreased a little within 4% after 10 days passed.

• Journal of the Korean Magnetics Society
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• v.3 no.4
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• pp.284-288
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• 1993

Low temperature magnetic properties and crystal structures of melt-spun $Sm_{2}Co_{7}B_{3}$ compound were characterized. The magnetic measurements in the temperature range 77 K~450 K indicated that a spin-reorientation took place at about 150~160 K. A large anisotropy was observed(Ha=135 kOe at 300 K, 725 kOe at 77 K) for $Sm_{2}Co_{7}B_{3}$ although the magnetic moment is rather low. The crystal structure of the $Sm_{2}Co_{7}B_{3}$ compound was analyzed in detail by Rietveld analysis of powder diffraction pattern, and it was revealed that B(4h) atoms are not placed in the Sm(2e) layer but in between the Sm(2e) and Co($6i_{1}$) layers.

• Journal of Magnetics
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• v.8 no.3
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• pp.124-127
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• 2003

HDDR (hydrogenation, disproportionation, desorption, recombination) and mechanical milling processes have been applied to the $SmCo_{5}$ alloy in an attempt to produce a highly coercive powder. The $SmCo_{5}$ alloy had very high structural stability under the hydrogen atmosphere and the 1:5 phase was only partially disproportionated under up to 10 kgf/$\textrm{cm}^2$ hydrogen gas. The partially disproportionated material was recombined not into 1:5 phase after the HDDR, but rather into multi-phase mixture consisting of 1:5, 2:17, 2:7 and 1:7 phases. The $SmCo_{5}$ alloy HDDR-treated with hydrogen up to 10 kgf/$\textrm{cm}^2$ had poor coercivity. For a useful HDDR to prepare a high coercivity $SmCo_{5}$ alloy powder, much higher hydrogen pressure well exceeding 10 kgf/$\textrm{cm}^2$ would be required. The $SmCo_{5}$ alloy lump was amorphized by an intensive mechanical milling, and it was crystallised ultra-finely by a subsequent optimum annealing. The optimally annealed material had very high coercivity, and it was found that the mechanical milling followed by an annealing was an effective way of producing highly coercive $SmCo_{5}$ alloy powder.

• Journal of the Korean Magnetics Society
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• v.1 no.1
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• pp.17-24
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• 1991

Laves phases of $NdFe_2$, $Nd{(Fe_{0.5})}_2$, $SmCo_2$ and $Sm{(Fe_{0.5}Co_{0.5})}_2$ stoichiometry were prepared using a rapid solidification technology. Low temperature magnetic properties show ferromagnetic behaviors for the $Nd{(Fe_{0.5}Co_{0.5})}_2$, $SmCo_2$ and $Sm{(Fe_{0.5}Co_{0.5})}_2$Nd(Feo,Coo,) Laves compounds while a sort of spin reorientation has been suggested for the supposed composition of $NdFe_2$ alloy. This rapidly solidified $NdFe_2$ alloy is believed to consist of metastable rhombohedral $NdFe_7$ phase plus fine particles of Nd-rich phase. Some evidence of phase transition from the mixture of unstable $NdFe_7$ compound plus Nd-rich to $Nd_2Fe_{17}$ plus Fe-Nd-O phase was obtained after annealing the $NdFe_2$, alloy. The pseudo-binary Laves compound, $Sm{(Fe_{0.5}Co_{0.5})}_2$ exhibits a high coercivityof 4 kOe at room temperature with Curie temperature of $400^{\circ}C$ while the $Nd{(Fe_{0.5}Co_{0.5})}_2$ compound shows a magnetic moment of $2.8\;{\mu}_B/f.u.$.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.726-729
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• 1995

We investigated the effects of Sm on the microstructure and magnetic properties of Fe-Co Alloy films prepared by a DC triode sputtering. The magnetostriction was found to be changed with the Sm content from positive to negative values, taking a zero magnetostriction was at about 3 at% Sm. The Sm content dependence of magnetostriction was explained by the formation of Sm enriched amorphous phase surrounding the main bcc (Fe,Co) crystalline phase, which was observed by a high resolution transmission electron microscopy.

• Journal of Magnetics
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• v.6 no.4
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• pp.122-125
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• 2001

Phase relationships of the HDDR (hydrogenation, disproportionation, desorption and recombination)-treated Sm$_3$(Fe,M)$_{29}$-type alloy with chemical composition of Sm$_{9}$Fe$_{65}$ $Co_{20}$V$_{6}$ were studied by X-ray diffraction (XRD) and by thermomagnetic analysis (TMA). The alloy was disproportionated into a mixture of $SmH_{x}$ and $\alpha$-Fe at high temperature under hydrogen gas. The disproportionated material was recombined into a mixture of Sm-(Fe,M) (M = Co and/or V) and $\alpha$-Fe phases. The structure of the Sm-(Fe,M) phase was dependent upon the recombination conditions, and a detailed phase diagram showing the phase relationships in the HDDR-treated alloy has been established. The Sm-(Fe,M) phase in material recombined above $900^{\circ}C$ had the $Sm_2Fe_{17}$-type structure, and it exhibited the $SmFe_{7}$-type structure when recombined at temperatures ranging from $700^{\circ}C$ to $850^{\circ}C$. Recombination below $650^{\circ}C$ led to the $SmFe_3$-type structure of the Sm-(Fe,M) phase. Curie temperatures of the Sm-(Fe,M) phases in the recombined material were significantly higher than those of the corresponding stoichiometric phases. It was suggested that the chemical composition of the Sm-(Fe,M) phases may be significantly different from that of the corresponding stoichiometric phases. All the HDDR-treated $Sm_{9}Fe_{65}Co_{20}V_{6}$ materials showed the soft magnetic features regardless of the phase constitution.n.

• Korean Journal of Veterinary Service
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• v.23 no.1
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• pp.45-59
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• 2000

The present study was conducted to investigate the epidemiological properties of salmonellosis of poultry farms in Kyongbuk province during the relied from November 1998 to November 1999 And antibiotic susceptibility and biochemical characteristics of 120 Salmonella cultures isolated from chicken samples were also investigated. The results obtained through this study were summarized as follows, 1. Among 667,200 chickens of 31 flocks in 17 layer farms and 9 broiler farms, 61,350 chickens of 31 flocks were died with salmonellosis. The death rate of 25 farms varied from 0.1% to 75.0%, and the average death rate was 9.2%. 2. According to etiological agents, fowl typhoid was shown the most predominant outbreak among the salmonellosis during a year, which accounted for 8R.0%(22/25) of the total case 3. The serotypes of 120 Salmonella isolates were identified as 7 strains(5.8%) of S pullorum, 10 strains(8.4%) of S typhimurium and 103 strains(85.8%) of S gallinarum. 4. Most outbreak of fowl typhoid were prevalent on the layer chicken farms(77.1%), and the summer season(45.5%) also appeared the most hazardous season during the year. 5. It seemed that the Hyline breed(70.6%) was the most susceptible among the layer chicken breeds, and followed by Isabrown(23.5%), Tetra(5.9%) in order. 6. In layers, 76.4% of fowl typhoid occurred commonly from 14 to 40 weeks including the early laying peroid, but in broiler farms, all cases was outbreak within first second weeks. 7 All the strains of S pullorum were resistant to lincomycin(Lm), penicillin(Pm), and steptomycin(Sm), but sensitive to amikacin(Ak), ampicillin(Am), cephalothin(Ce), ciprofloxacin (CiP), chloramphenicol(Cm), colistin(Co), enrofloxacin(Enr), furazolidone(Fu), gentamicin(Gm), kanamycin(Km), neomycin(Nm), polymyxin(Po), and teracycline(Tc). All the strains of S typhimurium were resistant to Lm(100%), Pm(100%), Po(90%), and Sm(90%), but were sensitive to Ak, Am, Ce, CiP, Cm, Co, Enr, Fu, Gm, Km, Nm, and Tc. 8. Minimum inhibitory concentration(MIC) of 103 strains of S gallinarum were also evaluated and their patterns were much more variable than others. All the strains of S gallinarum were sensitive to Ak, Am, Ce, Cip, Cm, Enr, Fu, Km, and Nm, but resistant to Lm(100%), and Sm(100%), 99(96.1%) to Co, 83(80.6%) to Pm, and 83(80.6%) to Po, 55(53.4%) to Gm, and 33(32.0%) to Tc. 9. The multiple drug resistance patterns of 120 Salmonella strains were CoLmPmPo Sm pattern(34.2%), CoGmLmPmPoSmTc(20.8%), CoGmLmPmPoSm(13.3%), CoGmLmSm(7.5%), LmPmSm(7.5%), LmPm(6.7%), CoLmSmTc(3.3%),, CoGmLmSmTc(1.7%), GmLmSmTc(1.7%), CoGmLmPoSm(0.1%), LmPmPo(0.1%), CoLm Sm(0.1%), and LmSm(0.1%), in order.