• Journal of Magnetics
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• v.18 no.2
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• pp.86-89
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• 2013

This paper shows a new effective approach to measure crystallization temperature of soft magnetic underlayer (SUL) for next generation of heat assisted perpendicular recording media. This approach uses temperature dependent reflectivity, which shows a clear jump when samples are crystallized. To achieve this measurement, an optical system is set up using hot plate and infrared laser. Reflectivity of SUL $(Co_{70}Fe_{30})_{92}Ta_3Zr_5$ shows a clear jump at its amorphous-crystalline transition temperature. Experiment results show this effect is clear in infrared region, and is weak for visible light.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.339-341
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• 2007

Soft ferromagnetic materials are very useful for many sensors using magnetic materials with high permeability, low coercivity and low hysteresis loss. Among them, FeCoSiBNi amorphous magnetic films show us a good impedance change(about 3.05%/Oe, at 12MHz) by the exterior magnetic field in this experiment. These are produced by rapid solidification from the melt and the material is ejected in a jet from a nozzle and quenched in a stream of liquid. After that, we make them a shape of wire with different sizes of width. Thus, we can find that the impedance change (122.16%, at 12MHz) is occurred and the fabricated magnetic wire has the characteristics of good sensor element.

• Particle and aerosol research
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• v.6 no.1
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• pp.21-27
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• 2010

New process consisting of electrospray and epitaxial crystal growth processes was applied to the preparation of c-plane oriented barium ferrite ($BaFe_{12}O_{19}$) thin film for high density magnetic recording media. Sodium citrate aided process was proper to preparation of amorphous $BaFe_{12}O_{19}$ nanoparticles with geometric mean diameter of 3 nm and geometric standard deviation of 1.1. The electrospray was applicable to the prepare of amorphous $BaFe_{12}O_{19}$ thin film on a substrate, and the film thickness could be controlled by adjusting the electrospray deposition time. The c-plane oriented $BaFe_{12}O_{19}$ thin film was successfully prepared by 3 step annealing process of the $BaFe_{12}O_{19}$ amorphous film on a sapphire($Al_2O_3$) substrate; annealing at $350^{\circ}C$ for 30 min, annealing at $500^{\circ}C$ for 30 min, and annealing at $700^{\circ}C$ for 60 min.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.550-552
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• 2003

We prepared $Co_{77}Cr_{20}Ta_3$ Magnetic layer for perpendicular magnetic recording media with introduce Two-step methode and Amorphous Si Underlayer on slide glass substrate. The thickness of magnetic layer were 100nm, and Underlayer were varied from 5 to 100 nm. The multi layer Properties of crystal structure were examined with XRD. Prepared thin films showed improvement of dispersion angle of c-axis orientation ${\Delta}{\theta}_{50}$ caused by inserting Buffer-layer and amorphous Si underlayer.

• Journal of the Korean Electrochemical Society
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• v.6 no.4
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• pp.236-241
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• 2003

Magnetic CoW thin film alloys were electrodeposited from citrate baths to investigate the resulting microstructure and magnetic properties. Deposit tungsten (W) content in the films electrodeposited at $70^{\circ}C$ were independent of current density, while coercivity decreased from hard $(H_{c,//}\~150\;Oe\;and\;H_{c.{\bot}}\;\~240\;Oe)$ to soft magnetic properties $(H_{c,//}\~20\;Oe\;and\;H_{c.{\bot}}\;\~30\;Oe)$ with increasing current densities from $10\;to\;100mA{\cdot}cm^2$, with deposit W content $(\~40\%)$ relatively unaffected by the applied current density. X-ray diffraction analysis indicated that hcp $Co_3W$ phases [(200), (201) and (220) planes] in the CoW films electrodeposited at $70^{\circ}C\;and\;10mA{\cdot}cm^{-2}$ were dominant, whereas amorphous CoW phases with small amount of hcp $Co_3W$ [(002) planes] were dominant with deposition at $70^{\circ}C\;and\;100mA{\cdot}cm^{-2}$. At intermediate current densities $(25\;and\;50mA{\cdot}cm^{-2}),\;hop\;Co_3W$ phases [(200), (002), (201) and (220)] were observed. The average grain size was measured to be 30 nm from Sheller formula. It is suggested that the change of the deposit coercivities in the CoW thin films electrodeposited at $70^{\circ}C$ is attributed to the change of microstructures with varying the current density. Nanostructured $Co_3W/amorphous-CoW$ multilayers were fabricated by alternating current density between 10 and $100 mA{\cdot}cm^{-2}$, varying the individual layer thickness. The magnetic properties of $Co_3W/amorphous-CoW$ multilayers were strongly dependent on the thickness of the alternating hard and soft magnetic thin films. The nanostructured $Co_3W/amorphous-CoW$ multilayers exhibited a shift from low to high coercivities suggesting a strong coupling effect.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.136-139
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• 1997

In this paper, we inveatigate frequency dependance of inductance effects of FeCoB amorphous magnetic films. First, amorphous magnetic film having near zero magnetostriction is the basic composition of (Fe$_{1-x}$ / $Co_{x}$)$_{79}$Si$_2$B$_{19}$ with x=0.94, 0.95 and in order to decrease magnetio . anisotropy, the film was annealed in 28$0^{\circ}C$/30min, 40$0^{\circ}C$/30min, 40$0^{\circ}C$/1hr with near crystallization temperature under non-magnetic field. As result of investigation, in case of x=7.95 than x=0.94, we could have obtained high values, which inductance ratios in the low frequency was 488%. And Quality factor Q was under 0.7 in all sample, in case of annealed in 28$0^{\circ}C$/30min, we could have obtained highest value, which x=0.9fl is about 0.62 in 400[kHz], and in case of x=0.95 was about 0.35 in 1[MHz].z].].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.27-30
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• 1996

In this paper, we prove through the experiments the possibility that Co-amorphous magnetic films can be used as high sensibility materials. We fabricate amorphous film of Fe$\sub$4.7/Co$\sub$74.3/Si$_2$B$\sub$19/ by using sputtering method at high frequency. Then, we not only measure the magnetic Properties of the annealed samples, but also observe the magnetic domain by using an Kerr effect optical-microscope. As the result, we find that the samples have high sensibility

• Journal of Sensor Science and Technology
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• v.16 no.5
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• pp.389-393
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• 2007

Soft ferromagnetic materials are very useful for many sensors using magnetic materials demanding high permeability, low coercivity and low hysteresis loss. Among them, FeCoSiBNi amorphous magnetic films show a good impedance change (about 5.01 %/Oe, at 10 MHz) by the exterinal magnetic field in this experiment. The magnetic films are produced by melt-spun method, one of the rapid solidification process. Ribbon shape wires were made from the films, and let them annealed in DC magnetic field to increase the maximum Giant Magneto Impedance ratio. Field annealing decreases the stress and changes the effective anisotropy. Thus, we can find that the impedance change (200.47 %) is improved and the fabricated magnetic wire has characteristics of good sensor element.

• Journal of Magnetics
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• v.2 no.3
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• pp.76-85
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• 1997

Magnetic and magnetostrictive properties of Tb-Fe and Tb-Fe-B thin films are systematically investigated over a wide composition range from 40.2 to 68.1 at. % Tb. The films were fabricated by rf magnetron sputtering using a composite target which consists of an Fe plate and Tb chips. The microstructure, examined by X-ray diffraction, mainly consists of an amorphous phase and, at high Tb contents, a pure Tb phase also exists. A progressive change in the direction of anisotropy from the perpendicular to in-plane occurs as the Tb content increases and the boundary at which the anisotropy change occurs shifts significantly towards to higher Tb contents with the addition of B. The saturation magnetization exhibits maxima at the Tb contents of 42 and 48 at. % for Tb-Fe and Tb-Fe-B thin films, respectively, and it is decreased by the addition of B. The coercive force, measured in the easy direction, decreases monotonically with the Tb content. Excellent magnetostrictive characteristics, particularly at low magnetic fields, are achieved in both Tb-Fe and Tb-Fe-B thin films; for example, a magnetostriction of 138 ppm is obtained in a Tb-Fe-B thin film at a magnetic field as low as 30 Oe. The excellent magnetostrictive properties of the present thin films are supported by the equally excellent magnetic softness, the coercivity below 10 Oe and a typical squared-loop shape with the saturation field as low as 1 kOe. Due to the excellent low field magnetostrictive characteristics, the present Tb-Fe based thin films are thought to be suitable for Si based microdevices.

• Journal of the Korean Magnetics Society
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• v.13 no.5
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• pp.193-197
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• 2003

To materialize the magnetoelastic devices, such as a highly functional sensor and a signal processing device, using the Fe base amorphous film which has both excellent soft magnetic and magnetostrictive properties, in this study, a new method to control the magnetic anisotropy of a highly magnetostrictive film using bias stress has been proposed and tested. The film pattern, which was stressed by its substrate bending, was subjected to annealing for relieving its stress. Successively, the compressive stress occurred by flattening the substrate was formed in the pattern. With the introduction of the residual compressive stress, the magnetization of the film pattern was aligned in the transverse direction through magnetoelasic coupling. The magnetic domain structure and magnetization curve of the film pattern of which magnetic anisotropy was controlled by the proposed method were presented to verify the availability of the method.