• Korean Journal of Metals and Materials
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• v.49 no.4
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• pp.329-333
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• 2011

To develop wide-band noise absorbers with a special design for low-frequency performance, this study proposes a tin oxide (Sn-O) thin films as the noise absorbing materials in a microstrip line. Sn-O thin films were deposited on polyimide film substrates by reactive sputtering of the Sn target under flowing $O_{2}$ gas, exhibiting a wide variation of surface resistance (in the range of $10^{0}-10^{5}{\Omega}$) depending on the oxygen partial pressure during deposition. The microstrip line with characteristic impedance of $50\Omega$ was used for the measurement of noise absorption by the Sn-O films. The reflection parameter $(S_{11})$ increased with a decrease of surface resistance due to an impedance mismatch at the boundary between the film and the microstrip line. Meanwhile, the transmission parameter $(S_{21})$ diminished with a decrease of surface resistance resulting from an Ohmic loss of the Sn-O films. The maximum noise absorption predicted at an optimum surface resistance of the Sn-O films was about $150{\Omega}$. For this film, greater power absorption is predicted in the lower frequency region (about 70% at 1 GHz) than in conventional magnetic sheets of high magnetic loss, indicating that Ohmic loss is the predominant loss parameter for the conduction noise absorption in the low frequency band.

• Journal of the Korean Ceramic Society
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• v.43 no.2 s.285
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• pp.79-84
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• 2006

We studied the microstructure and magnetic property of the pulsed DC magnetron sputtered $Zn_{\0.8}Co_{0.2}O$ film as a function of substrate temperatures. The X-ray patterns of the $Zn_{\0.8}Co_{0.2}O$ film showed a strong (002) preferential orientation at $500^{\circ}C$. The films with a crystallite size of 23-35 nm were grown in the form of nano-sized structure and this tendency was remarkable with increasing substrate temperature. The UV-visible result showed that the $Zn_{\0.8}Co_{0.2}O$ film prepared above $300^{\circ}C$ has a high optical transmittance of over $80\%$ in the visible region. The absorption bands were observed due to sp-d interchange action by $Co^{2+}$ complex ion and dd transition in the region from 500 to 700nm. The resistivity of the film was below $10^{-1}\;\Omega-cm\;above\;300^{\circ}C$. The AGM analysis results for the all films showed the magnetic hysteresis curves of ferromagnetic nature. The low electrical resistivity and room temperature ferromagnetism of ZnCoO thin films 'deposited above $300^{\circ}C$ suggested the possibility for the application to Diluted Magnetic Semiconductors (DMSs).

• Journal of Magnetics
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• v.3 no.2
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• pp.55-63
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• 1998

Magnetic and magnetostrictive properties of amorphous Sm-Fe and Sm-Fe-B thin films are systematically investigated over a wide composition range from 14.1 to 71.7 at.% Sm. The films were fabricated by rf magnetron sputtering using a composite target composed of an Fe (or Fe-B) plate and Sm chips. The amount of B added ranges from 0.3 to 0.8 at. %. The microstructure, examined by X-ray diffraction, mainly consists of an amorphous phase in the intermediate Sm content range from 20 to 45 at.%. Together with an amorphous phase, crystalline phases of Fe and Sm also exist at low and high ends of the Sm content, respectively. Well-developed in-plane anisotropy is formed over the whole compositionrange, except for the low Sm content below 15 at.% and the high Sm content above 55 at %. As the Sm content increases, the saturation magnetization decreases linearly and the coercive force tends to increase, with the exception of the low Sm content where very large magnitudes of the saturation magnetization and the coercive force are observed due to the existence of the crystalline $\alpha$-Fe phase. The coercive force is affected rather substantially by the B addition, resulting in lower values of the coercive force in the practically important Sm content range of 30 to 40 at.%. Good magnetic softness indicated by well-developed in-plane anisotropy, a square-shaped hysteresis loop and a low magnitude of the coercive force results in good magnetostrictive characteristics in both Sm-Fe-B thin films. The magnetostrictive characteristics, particularly at low magnetic fields, are further improved by the addition of B; for example, at a magnetic field of 100 Oe, the magnitude of magnetostriction is -350 ppm in a Sm-Fe thin film and it is -470 ppm in a B containing Sm-Fe thin film.

• Journal of the Korean Magnetics Society
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• v.8 no.5
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• pp.261-269
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• 1998

Induced anisotropy with the energy of $6{\times}10^4\; J/m^3$ is obtained in amorphous Sm-Fe based thin films which are fabricated by rf magnetron sputtering under a magnetic field of 500~600 Oe. Compared with conventional thin films, the anisotropic thin films exhibit a similar "saturation" magnetostriction, but show a very large anisotropy in magnetorstiction which is of significant practical importance due to increased strain at a particular direction. It is shown from a systematic investigation over a wide composition range for binary Sm-Fe alloys that anisotropy is also induced, though small, during a normal sputtering procedure due to the stray field, and the largest anisotropy is observed in the composition range of 25~30 at.% Sm. Furthermore, induced anisotropy is also found to be formed by magnetic annealing, but the anisotropy energy is much smaller than that by magnetic sputtering. This may be because the volume diffusion by which atoms move during magnetic annealing to from induced anisotropy is much slower than the surface diffusion which is expected to be a dominant factor during magnetic sputtering.puttering.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.267-270
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• 2003

We have studied the interfacial diffusion phenomena and the role of ${\alpha}-Al_2O_3$ buffer layer as a diffusion barrier in the $Ba-ferrite/SiO_2$ magnetic thin films for high-density recording media. In the interface of amorphous Ba-ferrite ($1900-{\AA}-thick)/SiO_2$ thin film during annealing, the interfacial diffusion started to occur at ${\sim}700^{\circ}C$. As the annealing temperature increased up to $800^{\circ}C$, the interfacial diffusion abruptly proceeded resulting in the high interface roughness and the deterioration of the magnetic properties. In order to control the interfacial diffusion at the high temperature, we introduced ${\alpha}-Al_2O_3$ buffer layer ($110-{\AA}-thick$) in the interface of $Ba-ferrite/SiO_2$ thin film. During the annealing of $Ba-ferrite/{\alpha}-Al_2O_3/SiO_2$ thin film even at ${\sim}800^{\circ}C$, the interface was very smooth. The smooth interface of the film was also clearly shown by the cross-sectional FESEM. The magnetic properties, such as saturation magnetization 3nd intrinsic coercivity, were also enhanced, due to the inhibition of interfacial diffusion by the ${\alpha}-Al_2O_3$ buffer layer. Our study suggests that the ${\alpha}-Al_2O_3$ buffer layer act as a useful interfacial diffusion barrier in the $Ba-ferrite/SiO_2$ thin films.

• Journal of the Korean Magnetics Society
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• v.5 no.6
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• pp.921-927
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• 1995

The micro particle,s shapes of the magnetic films obtained by electrode position of Iron ions and Cobalt-Iron mixed ions in aluminum anodic oxidized films are dependent on the size of particle diameter. When the diameter of deposited particles is larger than $300\AA$, the film plane anisotropy caused by bottom extremity increases, and the crystalization orientation of FeC deposited unusually in the part of the bottom extremities affects on the coercive force Hc and the magnetic anisotropy energy Ku. It was confirmed that the shape anisotropy of particle affects on the both Hc and Ku because the FeC did not deposit in the Iron deposited samples entirely, but in the Cobalt-Iron alloy deposited samples, the effects by the very strong crystalization orientation of the FeC is larger than that of the shape anisotropy. From these results, the Cobalt-Iron alloyed films could switchover the film plane magnetic anisotropy to the perpendicular magnetic anisotropy energy by using the constrainting method of FeC deposition with Cu deposition instead of Cobalt-Iron alloy in the bottom extremities.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.239-239
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• 2003

As a result of the recent miniaturization and enhancement in the performance of thin film inductors and thin film transformers, there are increased demands for the thin films with a high magnetic permeability in the high frequency range, a high saturation magnetization, a high electrical resistivity, and a low coercive force. In order to improve high frequency properties, we will investigate anisotropy field by shape and size of pattern. The Fe-Al-O thin films of 16mm diameter and 1$\mu\textrm{m}$ thickness were deposited on Si wafer, using RE magnetron reactive sputtering technique with the mixture of argon and oxygen gases. The fabricating conditions are obtained in the working partial pressure of 2m Torr, O$_2$ partial Pressure of 5%, Input power of 400w, and Al pellets on an Fe disk with purity of 99.9%. For continuous thin film is the 4Ms of 19.4kG, H$\sub$c/ of 0.6Oe, H$\sub$k/ of 6.0Oe and effective permeability of 2500 up to 100MHz. In this work, we expect to enhanced effect of magnetic anisotropy on patterned of Fe-Al-O thin films.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.834-838
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• 1996

The diagnosis of the plasma in the facing targets sputtering system was performed in mixture gas of Ar 0.18-0.0 Pa, Xe 0.0-0.18 Pa and $O_2$ 0.02 Pa by using Langmiur's probe and the effect of plasma-damage to surface smoothness and magnetic characteristics of Ba ferrite films was clarified. The electron density $N_e$ and the electron temperature $T_e$ were evaluated at the center of the plasma and at the neighborhood of the anode ring. $T_e$ decreased and $N_e$ increased with increase of $P_{Xe}$ at the center of plasma. For the measurement at the neighborhood of the anode ring, $T_e$ was almost constant and $N_e$ took the minimum value at $P_{Xe}$ of 0.1 Pa, where Ba ferrite films with excellent c-axis orientation and magnetic characteristics were obtained. It was suggested that the restriction of the bombardment of recoiled particles as well as the suppress of plasma-damage were effective for obtaining good surface smoothness and excellent magnetic characteristics and it was useful for decreasing the crystallization temperature of Ba ferrite films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.103-106
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• 2002

We prepared $Co_{77}Cr_{20}Ta_{3}$ thin film with Facing Targets Sputtering Apparatus. which can deposit a high quality thin film CoCrTa magnetic layer for Perpendicular magnetic recording media. In order to obtain Good Crystal orientation of CoCrTa thin films. We prepared Thin Films on slide glass substrate. The thickness of Buffer-layer were varied from 10 to 50 nm and Magnetic layer thickness fixed 100[nm]. input current was varied from 0.2[A] to 0.5[A]. Substrate temperature was varied from room temperature to ${250^{\circ}C}$ respectively. The crystal orientation of the CoCrTa film were examined with XRD. Introduce Buffer-layer thin films showed improvement of dispersion angle of c-axis orientation (${\Delta\theta}_{50}$).

• Journal of Magnetics
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• v.1 no.1
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• pp.46-50
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• 1996

Highly oriented ${BaFe_{12}{O_{19}$ films were obtained by a KrF excimer laser ablation technique using (110)$(012){Al_2}{O_3}$(001)$(012){Al_2}{O_3}$ and $(012){Al_2}{O_3}$ substrates, respectively.The degree of alignment of more than 95% were achieved for (100) on (110)$(012){Al_2}{O_3}$ and (001)$(001){Al_2}{O_3}$ planes, and heteroepitaxial films of (114) on (012)$(012){Al_2}{O_3}$were possible to be grown with a lasing energy density of 6.67 J/$cm^2$ at an oxygen partial pressure ${PO_2}$ of 900 mTorr. The best magnetic properties were obtained from the as-deposited films at the substrate temperature of $700^{\circ}C$, and post annealing treatment was not needed to enhance the magnetic properties. Experimentally saturated magnetization ($4_pi M_S$) of 3600~3800 Gauss and coercivities $(H_c)$ of 3050~3080 Oe, which approach 85% of those of Ba-ferrite bulk composed of single domain particles, were obtained in this study.