• Title/Summary/Keyword: Vibrating sample magnetometer

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Characteristics of the Angular-dependent Exchange Coupling Bias in Multilayer [Pt/Co]N-IrMn with Toward-in Plane Applied Fields (박막수직방향에서 면방향으로 회전하는 인가자기장에 대한 다층박막 [Pt/Co]N-IrMn의 교환바이어스의 각도의존특성)

  • Kim, S.S.;Yim, H.I.;Rhee, J.R.;Lee, S.S.;Hwang, D.G.
    • Journal of the Korean Magnetics Society
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    • v.18 no.4
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    • pp.142-146
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    • 2008
  • The angular dependence of the exchange bias($H_{ex}$) and coercivity($H_c$) in multilayer $[Pt/Co]_N-IrMn$ with applied measuring field rotated toward in-plane at angle $\theta$ from perpendicular-to-plane, has been measured. Multilayer films consisting of $Si/SiO_2/Ta(50)/Pt(4)/[Pt(15)/Co(t_{Co})]_N/IrMn(50)/Ta(50)(in\;{\AA})$ were prepared by magnetron sputtering under typical base pressure below $2{\times}10^{-8}$ Torr at room temperature. Magnetization measurements were performed on a vibrating sample magnetometer and extraordinary Hall voltage measurement systems after cooling from 550 K under a field of 2 kOe applied along the perpendicular to film direction. The hysteresis loop shifts from the origin not only along the field axis but also along the magnetization axis. $H_{ex}$ and $H_c$ show a $1/cos{\theta}$ and $1/|cos{\theta}|$ dependence on the angle($\theta$) between the applied measuring field and the perpendicular-film direction, respectively. This $1/cos{\theta}$ dependence can be accounted for by considering the angular dependence of strong out-of-plane magnetic anisotropy introduced during the field cooling.

Synthesis and Magnetic Property of Nanocrystalline Fe-Ni-Co Alloys during Hydrogen Reduction of Ni0.5Co0.5Fe2O4 (Ni0.5Co0.5Fe2O4의 수소환원에 의한 나노구조 Fe-Ni-Co 합금의 제조 및 자성특성)

  • Paek, Min Kyu;Do, Kyung Hyo;Bahgat, Mohamed;Pak, Jong Jin
    • Korean Journal of Metals and Materials
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    • v.49 no.2
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    • pp.167-173
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    • 2011
  • Nickel cobalt ferrite($Ni_{0.5}Co_{0.5}Fe_2O_4$) powder was prepared through the ceramic route by the calcination of a stoichiometric mixture of NiO, CoO and $Fe_2O_3$ at $1100^{\circ}C$. The pressed pellets of $Ni_{0.5}Co_{0.5}Fe_2O_4$ were isothermally reduced in pure hydrogen at $800{\sim}1100^{\circ}C$. Based on the thermogravimetric analysis, the reduction behavior and the kinetic reaction mechanisms of the synthesized ferrite were studied. The initial ferrite powder and the various reduction products were characterized by X-ray diffraction, scanning electron microscopy, reflected light microscope and vibrating sample magnetometer to reveal the effect of hydrogen reduction on the composition, microstructure and magnetic properties of the produced Fe-Ni-Co alloy. The arrhenius equation with the approved mathematical formulations for the gas solid reaction was applied to calculate the activation energy($E_a$) and detect the controlling reaction mechanisms. In the initial stage of hydrogen reduction, the reduction rate was controlled by the gas diffusion and the interfacial chemical reaction. However, in later stages, the rate was controlled by the interfacial chemical reaction. The nature of the hydrogen reduction and the magnetic property changes for nickel cobalt ferrite were compared with the previous result for nickel ferrite. The microstructural development of the synthesized Fe-Ni-Co alloy with an increase in the reduction temperature improved its soft magnetic properties by increasing the saturation magnetization($M_s$) and by decreasing the coercivity($H_c$). The Fe-Ni-Co alloy showed higher saturation magnetization compared to Fe-Ni alloy.

Ti-Getter Effects on Magnetic Properties of Ti0.96Co0.02Fe0.02O2 (Ti-Getter가 Ti0.96Co0.02Fe0.02O2의 자기적 특성에 미치는 영향)

  • Nam, H.D.;Kim, S.J.;Baek, J.K.;Lee, S.R.;Park, Cheol-Su;Kim, E.C.
    • Journal of the Korean Magnetics Society
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    • v.18 no.3
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    • pp.109-114
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    • 2008
  • The samples were synthesized by using a solid state reaction. The X-ray diffraction pattern for $Ti_{0.96}Co_{0.02}Fe_{0.02}O_2$ showed a pure rutile phase with tetragonal structure, Mixtures of the proper proportions of the elements sealed in evacuated quartz ampoule were heated at $870{\sim}930^{\circ}C$ for one day and then slowly cooled down to room temperature at a rate of $10^{\circ}C$/h. In order to obtain single phase material, it was necessary to grind the sample after the first firing and to press the powders into pellets before annealing them for a second time in evacuated and sealed quartz ampoule. Magnetic properties have been investigated using the vibrating sample magnetometer (VSM). Room temperature magnetic hysteresis (M-H) curve showed an obvious ferromagnetic behavior and the magnetic moment per Fe atom under the applied of 0.8 T was estimated to be about $1.5\;{\mu}_B$/CoFe. But the magnetic moment per Fe atom under the applied of 0.8 T was estimated to be about $0.02\;{\mu}_B$/CoFe without Ti-getter. Size of particles is about $1\;{\mu}m$ using the transmission electron microscope (TEM). The ingredients of sample are distributed irregular in particles. Only Fe get shown on the surface of particles.

Magnetic Properties of $ThMn_{12}-type$$NdFe_{10.7}Ti_{1.2}Mo_{0.1}$>$Ti_{1.2}Mo_{0.1}$ ($ThMn_{12}$$NdFe_{10.7}Ti_{1.2}Mo_{0.1}$의 미세구조 및 자기적 성질 연구)

  • 안성용;이승화;김철성;김윤배;김창석
    • Journal of the Korean Magnetics Society
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    • v.7 no.2
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    • pp.90-96
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    • 1997
  • We have studied crystallographic and magnetic properties of $NdFe_{10.7}Ti_ {1.2}Mo_{0.1}$ by Mossbauer spectroscopy, X-ray diffraction and vibrating sample magnetometer (VSM). The alloys were prepared by arc-melting under an argon atmosphere. The $NdFe_{10.7}Ti_{1.2}Mo_{0.1}$ has pure a single phase, whereas $NdFe_{10.7}Ti_{1.3}$ contains some $\alpha$-Fe, conformed with X-ray diffractometry and Mossbauer measurements. The $NdFe_{10.7}Ti_ {1.2}Mo_{0.1}$ has a $ThMn_{12}-type$ tetragonal structure with $a_0=8.637{\AA}$ and $c_0=4.807{\AA}$. The Curie temperature ($T_c$) is 600 K from the result of Mossbauer measurement performed at various temperatures ranging from 13 to 800 K. Each spectrum of below $T_c$ is fitted with five subspectra of Fe sites in the structure ($8i_1, 8i_2, 8j_2, 8j_1, 8f$). The area fractions of the subspectra at room temperature are 12.3%, 14.0%, 21.0% 11.8%, 40.9%, respectively. Magnetic hyperfine fields for the Fe sites decrease in the order, $H_{hf}(8i)>H_{hf}(8j)>H_{hf}(8f)$. The abrupt changes in the magnetic hyperfine field, an magnetic moment observed at about 160 K in $NdFe_ {10.7} Ti_{1.2}Mo_{0.1}$ are attributed to spin reorientations. The average hyperfine field of the $NdFe_{10.7}Ti_{1.2}Mo_{0.1}$ shows a temperature dependence of $[H_{hf}(T)-H_{hf}(0)]/H_{hf}(0)=-0.34(T/T_C)^{3/2}-0.14(T/T_C)^{5/2}$ for $T/T_c<0.7$, indicative of spin wave excitation. The Debye temperatures of $NdFe_{10.7}Ti_{1.2}Mo_{0.1}$ is found to be Θ=340$\pm$5 K.

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Mössbauer Study of Tb2Bi1GaxFe5-xO12(x=0, 1) (Tb2Bi1GaxFe5-xO12(x=0, 1)의 뫼스바우어 분광연구)

  • Park, Il-Jin;Kim, Chul-Sung
    • Journal of the Korean Magnetics Society
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    • v.18 no.2
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    • pp.67-70
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    • 2008
  • $Tb_2Bi_1Ga_xFe_{5-x}O_{12}$(x=0, 1) fabricated by sol-gel and vacuum sealed annealing process. $Tb_2Bi_1Ga_xFe_{5-x}O_{12}$(x=0, 1) have been studied by x-ray diffraction(XRD), vibrating sample magnetometer, and $M\ddot{o}ssbauer$ spectroscopy. The crystal structures were found to be a cubic garnet structure with space group Ia3d. The determined lattice constants $a_0$ of x = 0, and 1 are $12.497\AA$, and $12.465\AA$, respectively. The distribution of gallium and iron in $Tb_2Bi_1Ga_xFe_{5-x}O_{12}$ is studied by Rietveld refinement. Based on Rietveld refinement results, the terbium and bismuth ions occupy the 24c site, iron ions occupy the 24d, l6a site, and nonmagmetic gallium ions occupy the 16a site. In order to verify the magnetic site occupancy of iron and gallium, we have taken $M\ddot{o}ssbauer$ spectra for $Tb_2Bi_1Ga_xFe_{5-x}O_{12}$(x=0, 1) at room temperature. From the results of $M\ddot{o}ssbauer$ spectra analysis, the absorption area ratios of Fe ions for $Tb_2Bi_1Fe_5O_{12}$ on 24d and 16a sites are 60.8 % and 39.2 %, respectively, and the absorption area ratios of Fe ions for $Tb_2Bi_1Fe_5O_{12}$ on 24d and 16a sites are 74.7 % and 25.3 %, respectively. It is noticeable that all of the nonmagnetic Ga atoms occupy the 16a site by vacuum annealing process.

The Effect of Non Magnetic ion Substitution for the FeCr2-xMxS4(M=Ga, In) by Mossbauer Spectroscopy (비자성 이온 Ga, In이 치환된 유화물 스피넬의 뫼스바우어 분광학 연구)

  • Son, Bae-Soon;Kim, Sam-Jin;Kim, Chul-Sung
    • Journal of the Korean Magnetics Society
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    • v.16 no.1
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    • pp.6-10
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    • 2006
  • The sulphur spinel $FeCr_{2-x}M_xS_4$(M=Ga, In) have been studied with Mossbauer spectroscopy, x-ray diffraction (XRD), and vibrating sample magnetometer. The XRB patterns for samples $FeCr_{2-x}M_xS_4$(M=Ga, In: x=0.1, 0.3) reveal a single phase, which the Ga and In ions are partially occupied to the tetrahedral (A) site. The Neel temperature for the Ga substituted samples increases from 180 to 188 K, with increase from x=0.1 to 0.3. While, it decreases from 173 to 160 K, for the In substituted samples of the x=0.1 and 0.3, respectively. The Mossbauer spectra were collected from 4.2 K to room temperature. We have analyzed the Mossbauer spectra using eight Lorentzian lines fitting method for the $FeCr_{2-x}In_xS_4$(x=0.1) at 4.2 K, yielding the 1311owing results; $H_{hf}=146.0kOe,\;{\Delta}E_Q=1.88mm/s,\;\theta=36^{\circ},\;\phi=0^{\circ},\;\eta=0.6$, and R=1.9. The Ga ions enter into the both sites octahedral (B) and tetrahedral (A), simultaneously the same amounts of Fe ions migrate from the A to the B site, this result is an agreement with XRD results, too. The ${\Delta}E_Q$ of the A and B site in Mossbauer spectra of the samples $FeCr_{2-x}Ga_xS_4$(x=0.3) are 0.83 and 2.94mm/s, respectively. While they are 0.56 and 2.36mm/s for the $FeCr_{2-x}In_xS_4$(x=0.3). It is noticeable that the ${\Delta}E_Q$ for the Ga doped samples are larger than that of the corresponding In doped samples, in spite of the larger ionic radius for In ions. The bond lengths of Cr-S, for the Ga and In doped samples (x=0.3) are found to be 2.41 and $2.43\;{\AA}$, respectively. We interpret that the larger covalence effect from the smaller bond length induces a large asymmetric charge distribution. Finally, it gives a large quadrupole interaction.

Thickness Dependence of Amorphous CoSiB/Pd Multilayer with Perpendicular Magnetic Anisotropy (비정질 강자성체 CoSiB/Pd 다층박막의 두께에 따른 수직자기이방성 변화)

  • Yim, H.I.
    • Journal of the Korean Magnetics Society
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    • v.23 no.4
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    • pp.122-125
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    • 2013
  • Perpendicular magnetic anisotropy (PMA) is the phenomenon of magnetic thin film which is preferentially magnetized in a direction perpendicular to the film's plane. Amorphous multilayer with PMA has been studied as the good candidate to realization of high density STT-MRAM (Spin Transfer Torque-Magnetic Random Access Memory). The current issue of high density STT-MRAM is a decrease in the switching current of the device and an application of amorphous materials which are most suitable devices. The amorphous ferromagnetic material has low saturated magnetization, low coercivity and high thermal stability. In this study, we presented amorphous ferromagnetic multilayer that consists of an amorphous alloy CoSiB and a nonmagnetic material Pd. We investigated the change of PMA of the $[CoSiB\;t_{CoSiB}/Pd\;1.3nm]_5$ multilayer ($t_{CoSiB}$ = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 nm, and $t_{Pd}$ = 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 nm) and $[CoSiB\;0.3nm/Pd\;1.3nm]_n$ multilayer (n = 3, 5, 7, 9, 11, 13). This multilayer is measured by VSM (Vibrating Sample Magnetometer) and analyzed magnetic properties like a coercivity ($H_c$) and a magnetization ($M_s$). The coercivity in the $[CoSiB\;t_{CoSiB}\;nm/Pd\;1.3nm]_5$ multi-layers increased with increasing $t_{CoSiB}$ to reach a maximum at $t_{CoSiB}$ = 0.3 nm and then decreased for $t_{CoSiB}$ > 0.3 nm. The lowest saturated magnetization of $0.26emu/cm^3$ was obtained in the $[CoSiB\;0.3nm/Pd\;1.3nm]_3$ multilayer whereas the highest coercivity of 0.26 kOe was obtained in the $[CoSiB\;0.3nm/Pd\;1.3nm]_5$ mutilayer. Additional Pd layers did not contribute to the perpendicular magnetic anisotropy. The single domain structure evolved in to a striped multi-domain structure as the bilayer repetition number n was increased above 7 after which (n > 7) the hysteresis loops had a bow-tie shapes.

The Superconducting Properties of a High-Temperature Superconducting GdBCO-Coated Conductor (고온초전도 GdBCO 박막선재의 초전도 특성)

  • Yang, Seok Han;Song, Kyu Jeong
    • New Physics: Sae Mulli
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    • v.68 no.12
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    • pp.1293-1301
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    • 2018
  • The basic magnetic properties of commercially available High-$T_c$ Superconductor (HTS) GdBCO-coated conductor (GdBCO-CCs) were investigated by using physical property measurement system-vibrating sample magnetometer (PPMS-VSM). From the zero-field-cooled (ZFC) m(T) curve, the $T_c$ was found to be ~93 K. After removing the background m(H) data, we obtained both the net m(H) data and the ${\Delta}m_{irr}$. The $H_{irr}(T)$ coincided very well with the power-law relation $H_{irr}=H_{irr}(0)(1-T/T_c)^n$ with $$n{\sim_=}1.19$$. The magnetic flux behavior was investigated by using the ${\delta}$ values in the relationship $J_c{\propto}{\Delta}m_{irr}{\propto}H^{-{\delta}}$. A ${\delta}{\approx}0$ region denoting an independent magnetic flux pinning effect, a ${\delta}{\approx}0.6{\sim}1.2$ region representing a collective flux pinning effect due to the interaction, and a ${\delta}{\gg}2$ region representing freely moving magnetic fluxes caused by the Lorentz force were observed. The boundary line between ${\delta}{\approx}0$ and ${\delta}{\approx}0.6{\sim}1.2$ is denoted by a $H_1$, and the one between ${\delta}{\approx}0.6{\sim}1.2$ and ${\delta}{\gg}2$ is denoted by a $H_2$. The ${\delta}(T)$ was obtained in the region of $H_1$ < H < $H_2$. As the temperature was decreased, the ${\delta}$ value gradually decreased.