• Journal of Magnetics
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• v.11 no.4
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• pp.182-188
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• 2006

The search for high-density recording materials has been one of most active and vigorous field in the field of magnetism. $FePt-L1_{0}$ nanoparticle has emerged as a potential candidate because of its high anisotropy. In this paper, we provide an overview of recent work at Argonne National Laboratory that contributes to the ongoing dialogue concerning the relation between structure and properties of the FePt nanoparticle system. In particular we discuss the ability to control structure and properties via dosing with Cr. Cr-dosed FePt films were grown via molecular beam epitaxy and annealed at $550^{\circ}C$ in an ultrahigh vacuum chamber, and were studied with the surface magneto-optic Kerr effect (SMOKE), scanning electron microscopy (SEM) and x-ray magnetic circular dichroism (XMCD). We found that small dosage of Cr helps to generate $L1_{0}$ phase FePt magnetic nanoparticles with small size, defined shape and regular spatial distribution on MgO (001) substrate. The nanostructures are ferromagnetic with high magnetic coercivity (${\sim}0.9T$) and magnetic easy axis in the desired out-of-plane orientation. We also show that controlling the lateral region where nanostructures exist is possible via artificial patterning with Cr.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.10
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• pp.1158-1165
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• 1988

In this paper, the polarization properties of spun fiber due to intrinsic birefringence and magneto-optic effects are theoretically analyzed and experimented. The degree of polarization which indicates the intrinsic birefrigence is measured over 0.818, and the variation of output polarization angle with input polarization angle is measured within 9$^{\circ}$. Compared with single mode fiber, spun fiber is found to have very excellent polarization-maintaining property. Implemented current measurement system using spun fiber can linearly measure the magnetic field up to 20,000 A/m generated by solenoid.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.41-41
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• 1998

Rare earth metal films have been used as a buffer layer for growing ferroelectric t thin film or a seed layer for magnetic multilayer. But when it was deposited on s semiconductor substrates for the application of magneto-optic (MO) storage media, it i is difficult to exactly measure magnetic cons떠nts due to shunting current, and so it n needs to grow metal films on insulator substrate to reduce such effect. Recently, it w was reported that ultra-thin Pt layer were epitaxially grown on A12O:J by ion beam s sputtering in 비떠 high vacuum and it can be used as a seed layer for the growth of C Co-contained magnetic multilayer. In this stu$\phi$, Pt thin film were epi떠xially grown on AI2D3 ($\alpha$)OJ) by RF magnetron s sputtering. The crystalline structure was analyzed by transmission electron microscope ( (TEM) and Rutherford Back Scattering (RBS)/Ion Channeling. In TEM study, Pt was b believed to be twinned on AI잉3($\alpha$)01) su$\pi$ace about Pt(ll1) plane.Moreover, RBS c channeling spectra showed that minimum scattering yield of Pt(111)/AI2O:J(1$\alpha$)OJ) was 4 4% and Pt(11J)/AI2D3($\alpha$)OJ) had 3-fold symmetry.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.350-350
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• 2011

The spin structure of Fe over layers on Cu (001), especially in region II is one of the unsolved problem for many years. We study the out - of - plane (OP) Fermi surfaces (FSs) of 7 monolayer Fe/Cu (001) films using angle resolved photo emission spectroscopy (ARPES). Ultrathin Fe was grown on Cu (001) substrate at room temperature and the experimental measurements were carried out at room temperature and low temperature. Fermi surfaces measured about $\frac{1}{4}$ of the Brillouin Zone (BZ) using photon energies ranging from 170 eV to 280 eV. Our results confirmed that ferromagnetic signal at 7 ML Fe on Cu (001) is nearly zero. These results are consistent with our recent x-ray magnetic circular dichroism (XMCD) and surface magneto - optic Kerr effect (SMOKE) experiments. Based on our observations we have made a simple model of this system, which explains all the experimental results.

• Journal of Magnetics
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• v.10 no.2
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• pp.41-43
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• 2005

We have investigated an optical waveguide isolator with a multimode interference section by wafer direct bonding, operating at a wavelength $1.55\;{\mu}m$. In order to fabricate the device for monolithic integration, the wafer direct bonding between a magnetic garnet material as a cladding layer and a semiconductor guiding layer has been achieved. We found that wafer direct bonding between InP and GGG $(Gd_3Ga_5O_{12})$ is effective for the integration of a waveguide optical isolator. The isolation ratio was obtained to be 2.9 dB in the device.

• Journal of Magnetics
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• v.2 no.4
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• pp.147-156
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• 1997

An artificially modulated magnetic Co/Pd multilayer is one of the promising candidates for high density magneto-optic (MO) recording media, due to a large Kerr rotation angle in the wavelength of a blue laser beam. However, since multilayer structure, as well as amorphous structure, is a non-equilibrium state in terms of free energy and a MO recording technology is a kind of thermal recording which is conducted around Curie temperature (Tc) of the recording media, when the Co/Pd mulilayer is used for the MO recording media, changes in the magnetic properties are occurred as the amorphous structure do. Therefore, the assessment of the magnetic properties in the Co/Pd multilayer during interdiffusion is crucially important both for basic research and applications. As the parameter of the magnetic properties in this research, saturation magnetization and perpendicular magnetic anisotropy energy of the Co/Pd multilayer are measured in terms of Ar sputtering pressure and heat treatment temperature. Form the results of the research, we find out that the magnetic exchange energy between Co and Pd sublayers strongly affects the changes in the magnetic properties of the Co/Pd multilayers during the interdiffusion in ferromagnetic state. This discovery will provide the understanding of the magnetic exchange energy in the Co/Pd multilayer structure and suggest the operating temperature range for MO recording in the Co/Pd multilayer for the basic research and applications, respectively.

• Journal of the Korean Magnetics Society
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• v.14 no.3
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• pp.105-108
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• 2004

Array of magnetic Ni nanostructures has been fabricated on Si substrate by using nanoporous alumina film as a mask during deposition. The nanostructures are truncated cone-shape and the lateral sizes are comparable to height. While the continuous film shows well-defined in-plane magnetization, the nanostructure shows perpendicular component of magnetization at remanence. The hysterectic behavior of nanostructures is dominated by the demagnetizing field instead of interaction among them.

• Journal of Magnetics
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• v.6 no.3
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• pp.86-89
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• 2001

Microstructure modifications are investigated for annealed Co-based amorphous ribbon in vacuum and open air. X-ray diffraction (XRD) spectra for annealed sample in vacuum indicate atomic arrangements with initial nucleation of hcp-Co crystallite at 38$0^{\circ}C$ annealing temperature. However, the XRD spectra in samples with long annealing times of $t_a\geq300$ min demonstrate sharp and good developed surface crystalline hcp-, fcc- Co and $Co_2$Si phases. The giant magnetoimpedance (GMI) profile at 0.1 MHz displaying one-peak behavior in vacuum annealed samples at T = 38$0^{\circ}C$ irrespective of annealing time $t_a$ from 20 to 480 mim. For the annealed samples in an open air, the GMI profile shows two-peaks for $t_a$ = 20 min annealed sample. However, one of peaks disappears and an asymmetric GMI profile exhibits a drastic step-like change near zero field for $t_a\geq300$min. Such asymmetric GMI characteristics is related to the surface microstructures of fcc-Co, hop-Co and $Co_2$Si crystalline phases.

• Journal of Magnetics
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• v.2 no.3
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• pp.86-92
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• 1997

An artificially modulated magnetic Co/Pd multilayer is one of the promising candidates for high density magneto-optic (MO) recording media in the wavelength of a blue laser beam, due to large Kerr rotation angle. However, since the Co/Pd multilayer is a non-equilibrium state in terms of free energy and MO recording is a kind of thermal recording which is conducted around Curie temperature (Tc) of the recording media, the assessment of the thermal stability in the Co/Pd multilayer is crucially important both for basic research and applications. As the parameter of the thermal stability in this research, effective interdiffusion coefficients (Deff) perpendicular to the interface of the Co/Pd multilayers are measured in terms of Ar sputtering pressure and heat treatment temperature. From the results of the research, we find out that the magnetic exchange energy between Co and Pd sublayers strongly affects Deff of the Co/Pd multilayers. This discovery will provide the understanding of the magnetic exchange energy in the effective interdiffusion process of a magnetic multilayer structure and suggest the operating temperature range for MO recording in the Co/Pd multilayer for the basic research and applications, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.141-141
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• 2000

In situ surface magneto-optic Kerr effect(SMOKE), X-ray photoelectron spectroscopy(XPS) and low energy electron diffraction(LEED) were used to study magnetic and structural properties of ultrathin Fe films grown on the Pd(111) surface. The SMOKE measurement showed strong enhancement of ferromagnetism after proper annealing process. Simultaneous changes in morphology was checked by LEED and XPS. After room temperature Fe deposition. longitudinal magnetization appeared above a critical thickness between 2.0 and 2.5 monolayers. When annealed at 450K, 2.0 monolayer Fe film exhibited boty longitudinal and polar magnetizations while 3.0 and 5.5 monolayer films showed little changes. After annealing at 600K, both magnetizations were totally destroyed in 2.0 monolayer film, but longitudinal magnetization was enhanced in 3.0 monolayer film. In the case of 5.5 monolayer film, it was only after 660K annealing that the enhancement of the longitudinal magnetization was observed. It was concluded that the surface flatness and the amount of intermixing were critical in the development of surface magnetism of this system.