• Journal of the Korean Magnetics Society
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• v.13 no.2
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• pp.53-58
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• 2003

Annealing effects of exchange bias fields ($H_{2ex}$(top), $H_{lex}$ (bottom)) on composite type NiFe/[FeMn/Mn]$_{80}$/NiFe multilayers have been studied. Three samples with ultra-thin Mn inserted layers on glass/Ta(50 $\AA$)/NiFe(150 $\AA$)/[F $e_{53}$M $n_{47}$(1.25 $\AA$)/Mn(0 $\AA$, 0.11 $\AA$, 0.3 $\AA$)]$_{80}$/NiFe(90 $\AA$)/Ta(50 $\AA$) were prepared by ion beam sputtering. The average x-ray diffraction peak ratios NiFe(111) of FeMn (111) fcc textures for the Mn inserted total thicknesses of 0 $\AA$, 9 $\AA$, and 24 $\AA$ were about 0.65, 0.90, and 1.5, respectively. For the sample without Mn inserted layer, the $H_{2ex}$ of 260 Oe up to 300 $^{\circ}C$ disappeared at 350 $^{\circ}C$. For two multilayer samples with ultra-thin Mn layers of 0.11 $\AA$ and 0.3 $\AA$, the $H_{2exs}$ of 310 Oe and 180 Oe up to 300 $^{\circ}C$ endured of 215 Oe and 180 Oe at 350 $^{\circ}C$, respectively. The $H_{ex}$ (bottom)s of three samples decreased from 100 Oe to 70 Oe up to 250 $^{\circ}C$, while these values increased beyond 300 $^{\circ}C$. This observation can be attributed to less diffusive path of Mn atoms in bottom NiFe than top NiFe layer. The top and bottom coercive fields slightly varied about 5 Oe∼10 Oe. From these results, we could obtain the enhancement of exchange coupling intensity and thermal stability by an ultra-thin Mn inserted layer on NiFe/[FeMn/Mn]$_{80}$/NiFe Multilayers.

• Korean Journal of Materials Research
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• v.6 no.6
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• pp.585-588
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• 1996

여러 가지 Zr합금에서 생성되는 석출물의 특성을 규명하기 위하여 시편을 $600^{\circ}C$에서 1시간 동안 열처리 한후 EDX가 부착된 TEM을 이용하여 석출물에 관한 연구를 수행하였다. Zr1.4Sn0.2Fe0.1Cr 합금에서는 두 종류의 석출물이 생성되는데 하나는 석출물의 대부분을 차지하는 HCP 구조으 Zr(Cr, Fe)2 석출물로서 이는 둥근 형태를 유지하며 결정립내나 결정립계에 관계없이 널리 분산되어 분포된다. 다른 하나의 석출물은 극히 일부에서만 관찰되는 Zr2(Fe, Si)성분의 석출물로서 이는 tetragonal 구조를 갖는다. Zr0.5Nb0.6Fe0.3V 합금에서는 tetragonal (Zr, Nb)2(Fe, V) 석출물이 형성되며, Nb이 1.0 wt.% 첨가된 Zr1.0Nb0.6Fe0.3V 합금에서는 HCP 구조의 (Zr, Nb)(Fe, V)2 석출물과 BCC 구조인 $\beta$-Zr이 생성된다. Zr1.0Nb0.6Fe0.3V합금을 제외하고는 대부분의 합금에서 석출물은 약 1.0$\mu\textrm{m}$의 크기를 나타냈다. 합금 조성이 다를 경우에 석출물 크기와 35$0^{\circ}C$ 부식 특성과는 부식 특성과는 연관성이 없는 것로 나타났다.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11b
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• pp.539-544
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• 1996

핵연료 피복관용 신합금으로 개발되고 있는 여러 가지 Zr합금에서 생성되는 석출물의 특성을 규명하기 위하여 EDX가 부착된 TEM을 이용하여 석출물에 관한 연구를 수행하였다. Zrl.4Sn0.2Fe0.1Cr 합금에서는 두 종류의 석출물이 생성되는데 하나는 석출물의 대부분을 차지하는 HCP 구조의 Zr(Cr,Fe)$_2$ 석출물로서 이는 둥근 형태를 유지하며 결정립내나 결정립계에 관계없이 널리 분산되어 분포된다. 다른 하나의 석출물은 극히 일부에서만 관찰되는 Zr$_2$(Fe,Si)성분의 석출물로서 이는 tetragonal 구조를 갖는다. Zr0.5Nb0.6Fe0.3V 합금에서는 tetragonal (Zr,Nb)$_2$(Fe,V)석출물이 형성되며, Nb이 1.0 wt.% 첨가된 Zr1.0Nb0.6Fe0.3V 합금에서는 HCP 구조의 (Zr,Nb)(Fe,V)$_2$ 석출물과 BCC 구조인 $\beta$-Zr이 생성된다. Zr1.0Nb0.6Fe0.3V 합금을 제외하고는 대부분의 합금에서 석출물은 약 1.0 $\mu$m의 크기를 나타냈다. 합금 조성이 다를 경우에 석출물 크기와 35$0^{\circ}C$ 부식 특성과는 연관성이 없는 것으로 나타났다.

• Journal of Powder Materials
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• v.11 no.6 s.47
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• pp.486-492
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• 2004

We report the crystallization and magnetic properties of non-equilibrium $Al_{0.6}(Fe_{x}Cu_{1-x})_{0.4}(x=0.25, 0.50, 0.75)$ alloy powders produced by rod-milling as well as by new chemical leaching. X-ray diffractometry, transmission electron microscopy, differential scanning calorimetry and vibrating sample magnetometry were used to characterize the as-milled and leached specimens. After 400 h or 500 h milling, only the broad peaks of nano bcc crystalline phases were detected in the XRD patterns. The crystallite size, the peak and the crystallization temperatures increased with increasing Fe. After being annealed at $600{^\circ}C$ for 1 h for as-milled alloy powders, the peaks of bcc $AlCu_{4}\;and\;Al_{13}Cu_{4}Fe_{3}\;for\;x=0.25,\;bcc\;AlCu_{4}\;and\;Al_{5}Fe_{2}\;for\;x=0.50,\;and\;Al_{5}Fe_{2},\;and\;Al_{0.5}Fe_{0.5}\;for\;x=0.75$ are observed. After being annealed at $500{^\circ}\;and\;600{^\circ}C$for 1 h for leached specimens, these non-equi-librium phases transformed into fcc Cu and $CuFe_{2}O_{4}$phases for the x=0.25 specimen, and into bcc ${\alpha}-Fe,\;fcc\;Cu,\;and\;CuFe_{2}O_{4}$ phases for both the x=0.50 and the x=0.75 specimens. The saturation magnetization decreased with increasing milling time for $Al_{0.6}(Fe_{x}Cu_{1-x})_{0.4}$ alloy powders. On cooling the leached specimens from $800{\~}850^{\circ}C$,\;the magnetization first sharply increase at about $491.4{\circ}C,\;745{\circ}C,\;and\;750.0{\circ}C$ for x=0.25, x=0.50, and x=0.75 specimens, repectively.

• Proceedings of the Korean Nutrition Society Conference
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• 2000.11a
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• pp.56-56
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• 2000

본 연구는 철분결핍과 caffeine섭취가 흰쥐의 혈당과 과산화에 미치는 영향을 알아보기 위해서 수행되었다. 생후 2주된 48마리의 Sprague-Dawley 수컷 흰쥐를 철분과 caffeine의 첨가 수준에 따라 6군으로 나누어 4주간 사육하였다(C0F0 : caffeine 0%, Fe 5 ppm diet, C1F0 : caffeine 1%, Fe 5 ppm diet, C4F0 : caffeine 4%, Fe 5 ppm diet, C0F1 : caffeine 0%, Fe 50 ppm diet, C1F1 : caffeine 0%, Fe 50 ppm diet, C4F1 : caffeine 0%, Fe 50 ppm diet).(중략)

• Journal of the Korean Magnetics Society
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• v.11 no.3
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• pp.85-96
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• 2001

Experimental magnetization-temperature curves for melt-spun ribbons of amorphous alloys (Dy$\_$0.33/Fe$\_$0.67/)$\_$1-x/B$\_$x/(x=0 ,0.05, 0.1, and 0.15) and (Sm$\_$0.33/Fe$\_$0.67/)$\_$1-x/B$\_$x/(x=0, 0.01, 0.02, and 0.03) (in atomic fraction) are fitted with theoretical equations based on the mean field theory in order to calculate exchange couplings between constituent elements as a function of the B content. In the case of the DyFe$_2$-B system, the sign of the exchange coupling between Dy and Fe is negative, indicating that the magnetization direction of Dy is antiparallel to that of Fe. The sign of the other two couplings are positive indicating a parallel alignment. The exchange coupling between Fe ions are greatest, while that between Dy ions is negligible. In the case of the SmFe$_2$B alloys, the sign of all the couplings are positive, indicating ferromagnetic coupling between the spins. The exchange couplings between Fe ions, and Fe and Sm are comparable to each other, but they are much greater than that between Sm ions. The high exchange coupling between Fe and Sm, which is considered to occur indirectly, is rather unexpected, but it is considered to be unique characteristics of amorphous Sm-Fe alloys. In both alloy systems, the exchange coupling between Fe ions increases with increasing B content. and this may be explained by the increase of the Fe-Fe separation with increasing B content. The exchange coupling between Fe and RE also increases with increasing B content. As the B content increases, the magnetization decreases over the whole temperature range, and the Curie temperature also decreases.

• Journal of the Korean Magnetics Society
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• v.8 no.6
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• pp.335-340
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• 1998

Colossal magnetoresistance $La_{0.67}Ca_{0.33}Mn_{0.99}^{57}Fe_{0.01}O_3$ material has been produced by a metal-salt routed sol-gel process method. Magnetic properties of $La_{0.67}Ca_{0.33}Mn_{0.99}^{57}Fe_{0.01}O_3$ have been studied with x-ray diffraction, Rutherford back-scattering spectroscopy(RBS), vibrating sample magnetometer, and Mossbauer spectroscopy. Crystalline $La_{0.67}Ca_{0.33}Mn_{0.99}^{57}Fe_{0.01}O_3$ was perovskite cubic structure with a lattice parameter $a_0=3.868$\AA$$. And there was no appreciable change in the value of the lattice parameter when a small amount (x=0.01) of iron was added. However, Mossbauer and VSM data indicate the Curie temperature of the $La_{0.67}Ca_{0.33}Mn_{0.99}^{57}Fe_{0.01}O_3$ decreased from 282 to 270 k and also the saturation magnetization from 84 to 81 emu/g at 77 K. Mossbauer spectra of $La_{0.67}Ca_{0.33}Mn_{0.99}^{57}Fe_{0.01}O_3$ have been taken at various temperatures ranging form 4.2 K to room temperature. Analysis of $^{57}Fe$ Mossbauer data in terms of the local configurations of Mn atoms has permitted the influence of the magnetic hyperfine interactions to be monitored. The isomer shifts show that the charge state of all Fe ions are ferric. The magnetoresistance of $La_{0.67}Ca_{0.33}Mn_{0.99}^{57}Fe_{0.01}O_3$ was about 33 % at semiconductor-metal transition temperature $T_{SC-M}=250K$.

• Journal of the Korean Magnetics Society
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• v.3 no.1
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• pp.18-22
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• 1993

The cationic distributions and magnetic properties of $Cu_{x}Zn_{1-x}Fe_{2}O_{4}(0{\leq}x{\leq}1)$ have been studied by X-ray diffraction and $M\"{o}ssbauer$ spectroscopy. The crystal structures are cubic spinels in the range $0{\leq}x{\leq}0.9$. The ionic distribution of ${(Zn_{1-x}Fe_{x})}_{A}{[Zn_{x}Fe_{2-x}]}_{B}O_{4}$, where x=0.1. The distribution of $Fe^{3+}$ ions was extracted from the $M\"{o}ssbauer$ spectra below Curie temperature in the whole range $0{\leq}x{\leq}1$. The number of $Fe^{3+}$ ions in the tetrahedral sites and Curie temperature of Cu-Zn ferrite increase with increasing Cu-concentration.

• Journal of the Mineralogical Society of Korea
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• v.9 no.2
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• pp.55-63
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• 1996

Epidote occurs as veinlets in the propylitic alteration zone of the Bobae clay deposit, Pusan, Korea. Its cell parameters apparently decrease with the contents of Al, Fe, and Ca. Fourier transform infrared (FTIR) spectra show one hydrosyl environment related to AlM2 at 3357-3358 cm-1. In the mid-infrared region, the peaks at 950 and 1030 cm-1 sharper with increasing Al shifting to higher energy region. The peak at 885 cm-1 shifts slightly to a lower energy region with a decreasing intensity as the Fe content increases. In the far-IR region, epidote exhibits absorption bands at 120 and 140 cm-1, which are related to the Ca-O bonds in A-sites.M ssbauer spectra of epidote show that the isomer shifts of Fe3+ range from 0.36-0.37 at the M3 site and from 0.35-0.44 at M1 site. Fe2+ shows the isomer shift ranging from 1.11 to 1.13. Quadrupole splitting is 2.04 for Fe3+M3, 0.52-0.70 for Fe3+M1, and 2.61-2.70 for Fe2+M3. Calculation shows Fe3+M386-90.7%, Fe3+M12.5-3.6%, and Fe2+M35.8-11.4% of total iron, showing preferential distribution of Fe3+ in the M3 site. The Fe3+M3 content is between 0.486 and 0.513 per formula unit. in the Fe-rich epidote, less Fe3+ and more Fe2+ are accommodated in the M1 and M3 sites. Hence, the overall disorder increases as total Fe content increase. The ordering parameter of the Bobae epidote is 0.93-0.95, suggesting a disequilibrium state below 200$^{\circ}C$. The constant temperature over a long period may be essential for the transition from disordered state to equilibrium state, despite the possible variation in flux and composition of the hydrothermal fluid.

• Bulletin of the Korean Chemical Society
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• v.15 no.8
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• pp.636-640
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• 1994

The nonstoichiometric perovskite solid solutions of the $Nd_{1-x}Sr_xFeO_{3-y}$ system for the compositions of x=0.00, 0.25, 0.50, 0.75, and 1.00 have been prepared at $1150^{\circ}C$ in the air pressure. The compound of x=0.00, NdFe$O_{3.0}$, contains only $Fe^{3+}$ ion in octahedral site and the others involves the mixed valence state between $Fe^{3+}$ and $Fe^{4+}$ ions. The mole ratio of $Fe^{4+}$ ion or the ${\tau}$-value increases steadily with the x-value and then is maximized at the compositionof x= 1.00. The nonstoichiometric chemical formulas of the system are formulated from the x, ${\tau}$ and y values. From the Mossbauer spectroscopy, the isomer shift of $Fe^{3+}$ ion decreases with the increasing x-value, which is induced by the electron transfer between the$Fe^{3+}$ and $Fe^{4+}$ ions. The transfer is made possible by the indirect interaction between $Fe^{3+}$ and$Fe^{4+}$ ions via the oxygen ion. The eg electrons of the$Fe^{3+}$ ions are delocalized over all the Fe ions. Due to the electron transfer, the activation energy of electrical conductivity is decrease with the increasing amount of $Fe^{4+}$ ion.