• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.5
• /
• pp.438-444
• /
• 2000

The prediction of mechanical properties for WC-Co alloys by evaluation of coercive force and magnetic saturation were studied in relation to their microstructure. The WC-8%Co alloys were prepared using different WC particle size, carbon content and various sintering temperature by PM process. The magnetic properties such as coercive force and magnetic saturation of sintered WC-Co alloys were critically dependent upon their final composition and microstructure. Slight changes of carbon contents and small variation of WC grain size result in marked changes of magnetic properties, hardness and transverse rupture strength of sintered WC-Co alloys. It was found that the coercive force and hardness were increased by fine WC grain size of sinterd alloys, and the coercive force was proportional to hardness. With decreasing total carbon content below the stoichiometric value in WC-8%Co alloys the volume fraction of $\eta$ phase increased steadily, while the magnetic saturation and transverse rupture strength decreased. The magnetic saturation was inversely proportional to the coercive force of WC-Co alloys.

• Korean Journal of Materials Research
• /
• v.8 no.6
• /
• pp.560-564
• /
• 1998

CoPtCr magnetic layer was fabricated on the Cr underlayer by RF magnetron sputtering and the protective $SiO_2$ layer was deposited at room temperature. As the thickness of Cr underlayer increased, the coercive force of magnetic layer increased, then saturated slightly further increasing Cr underlayer thickness. Maximum coercive force was 860 Oe. It is thought that in-plane arrangement of magnetic phase and magnetic decoupling between the magnetic crystallites could lead to the increase of the coercive force. Post-annealing raised the coercive force exceedingly. and maximum coercive force value was 1650 Oe which was acquired from the sample annealed at 55$0^{\circ}C$ for 1hr.

• Journal of the Korean Magnetics Society
• /
• v.4 no.2
• /
• pp.150-153
• /
• 1994

Magnetic field annealing method has been used to obtain proper hysteresis loop shapes which are useful to a device using amorphous ribbon. In this study, two pairs of Helmhotz coils were used to apply longitudinal and transverse magnetic field during annealing. For the measurement of coercive field strength noise which depends on magnetic field annealing, Co-based amorphous alloy ribbon $VITROVAC^{\circledR}$ 6030 was used. For the sample which was annealed under dc transverse and dc longitudinal magnetic field, coercive field strength noise was nearly independent of magnetizing frequency ranging from 1 to 100 kHz, but dc transverse and ac longitudinal magnetic fields annealed samples show that the coercive field strength noise decreased in power of magnetizing frequency. When magnetic domain nucleation occurred, the coercive field strength noise increased remarkably and decreased in power of magnetizing frequency.

• Proceedings of the KIEE Conference
• /
• 1993.07b
• /
• pp.1143-1146
• /
• 1993

The magnetic properties of aluminium anodized film in which Co-Fe alloy electrodeposited are investigated with regard to the alloy composition of magnetic films. The electrodeposited Co-Fe particles are confirmed to be single phase Co-Fe alloys by X-ray diffractions. The coercive force as well as the magnetic anisotropy energy can be controlled by changing the composition of the alloy. Magneticfilms having high saturation magnetization and high coercive force were obtained.

• Journal of the Korean Magnetics Society
• /
• v.10 no.3
• /
• pp.112-117
• /
• 2000

We inserted CoO layer in NiO spin-valves to improve on magnetoresistance and exchange coupling field. The magnetoresistance ratio was increased from 4.5 % to 5.5 % with the increase of CoO thickness. We can not find the dependence between (111) texture and exchange coupling by the measurement of XRD of CoO/NiO spin-valves. The surface roughness of CoO layer, 6.1 $\AA$ is twice more than that of NiO layer, 3.1 $\AA$. The increase of exchange coupling field and coercive field in the CoO/NiO spin-valves will be due to increasing roughness. We prepared the NiO/CoO/NiO/CoO/NiO spin-valves to reduce coercive field and the coercive field decreased from 110 Oe to 50 Oe, and the coupling field is not changed from 70 Oe.

• Journal of the Korean Ceramic Society
• /
• v.19 no.3
• /
• pp.223-228
• /
• 1982

For the preparation of ferroxidure BaO.5.5 $Fe_2O_3$ with high coercive force, the green and calcined coprecipitates, which were obtained by neutralizing the mixed salt solution $FeCl_2-BaCl_2$ and $FeCl_3-BaCl_2$ with alkali solution $NaOH-Na_2CO_3$, were investigated about the thermal reaction, crystal growth, and the magnetic properties of the sintered specimens. The very single-domain crystallites of Ba-ferrite with high coercive force are formed from the coprecipitate of amorphous $Fe(OH)_3$ and amorphous $BaCO_3$ at lower temperature than that of subnucleus crystalline $\delta$-FeOOH and amorphous $BaCO_3$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.05d
• /
• pp.90-95
• /
• 2003

The present paper is to investigate the phase stability and soft magnetic properties of amorphous CoNbZr films when Pd is added as a substitution for CoNbZr alloys. The films were prepared by a RF magnetron sputtering method. The CoNbZrPd films deposited on Si wafers exhibited amorphous structures being independent upon the amount of Pd added in the films. On the addition of 4.34% Pd, the excellent soft magnetic characteristics of the films were observed with a coercive force of 0.54 Oe and an anisotropy field of 11 Oe, whereas a coercive force of 1 Oe and an anisotropy field of 3.5 Oe were shown in the film without the addition of Pd. The increased anisotropy field and low coercive force of the films may be attributed to the occupancy of Pd in the preferred sites parallel to the external magnetic field applied on the deposition process. A permeability of about 1100 was kept constant in the operation frequency ranging up to 100 MHz, which can be explained by the Landau-Lifshitz formula.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
• /
• 2002.11a
• /
• pp.54-58
• /
• 2002

The present paper is to investigate the phase stability and soft magnetic properties of amorphous CoNbZr films when Pd is added as a substitution for CoNbZr alloys. The films were prepared by a RF magnetron sputtering method. The CoNbZrPd films deposited on Si wafers exhibited amorphous structures being independent upon the amount of Pd added in the films. On the addition of 4.34% Pd, the excellent soft magnetic characteristics of the films were observed with a coercive force of 0.54 Oe and an anisotropy field of 11 Oe, whereas a coercive force of 1 Oe and an anisotropy field of 3.5 Oe were shown in the film without the addition of Pd. The increased anisotropy field and low coercive force of the films may be attributed to the occupancy of Pd in the preferred sites parallel to the external magnetic field applied on the deposition process. A permeability of about 1100 was kept constant in the operation frequency ranging up to 100 MHz, which can be explained by the Landau-Lifshitz formula.

• Journal of Magnetics
• /
• v.4 no.2
• /
• pp.65-68
• /
• 1999

The M-type barium ferrite ($BaFe_{12}O_{19}$) is well known magnetic material to be used as a permanent magnet due to its strong uniaxial anisotropy. The substitution of nonmagnetic $Ti^{+4}$ and magnetically weak $Co+^2ion for Fe^{+3}$ to its strong uniaxial anisotropy. The substitution of nonmagnetic $Ti^{+4}$ and magnetically weak $Co+^2ion for Fe^{+3}$ sublattices reduces the uniaxial anisotropy and those compounds open a new application field of noise suppressor at high frequencies. In this study, the magnetic and microwave absorbing properties are investigated in Ti-and Co-substituted barium ferrites ($BaFe_{12-2X} Ti_XCo_XO_{19}$). The saturated magnetization decreases linearly with the substitution of Ti and Co. The rapid drop in coercive force is observed with Ti and Co substitution upto x=1.2. The magnetic permeability spectrum shows the natural magnetic resonance in the specimens with small coercive force and large attenuation of microwave is predicted in those specimens at high frequencies (above 4 GHz).

• Proceedings of the Korean Magnestics Society Conference
• /
• 1999.10a
• /
• pp.106-107
• /
• 1999