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이광은(K. E. Lee),느반더(L. V. Tho),김상훈(S. H. Kim),김철기(C. G. Kim),김종오(C. O. Kim) 한국자기학회 2006 韓國磁氣學會誌 Vol.16 No.4
Amorphous alloys of Co-rich magnetic amorphous films are well known as typical soft magnetic alloys. They are used for many kinds of electric and electronic parts such as magnetic recording heads, transformers and inductors. CoFeHfO thin films were prepared by RF magnetron reactive sputtering. The films were deposited onto Si(100) substrates with a power of 300W at room temperature. The reactive gas was introduced up to 10% (O₂/(Ar + O₂)) during deposition, and the Co<SUB>39</SUB>Fe<SUB>34</SUB>Hf<SUB>9.5</SUB>O<SUB>17.5</SUB> thin film exhibit excellent soft magnetic properties : saturation magnetization (4πM<SUB>s</SUB>) of 19 kG, magnetic coercivity (H<SUB>c</SUB>) of 0.37 Oe, anisotropy field (H<SUB>k</SUB>) of 48.62 Oe, and an electrical property is also shown to be as high as 300 μΩcm. It is assumed that the good soft magnetic properties of Co<SUB>39</SUB>Fe<SUB>34</SUB>Hf<SUB>9.5</SUB>O<SUB>17.5</SUB> thin film results from high electrical resistivity and large anisotropy field.
Mn 및 La - Mn 치환 Sr 페라이트의 자기적 특성 변화
장세동(S. D. Jang),김종오(C. O. Kim),김종희(J.H. Kim) 한국자기학회 2001 韓國磁氣學會誌 Vol.11 No.6
These experiments were carried out to examine the effects of elemental substitution of Mn and La-Mn on Sr-ferrite. The calcined properties for the Mn and La-Mn substitution were examined, and the sintered magnetic properties were compared with the stoichiometric condition. The magnetic properties of calcined SrM and (La-Mn)_(O.3)-SrM composition were as follows, respectively; Ms : 61.06 emu/g, iHc: 4.45 kOe and Ms : 61.16 emu/g, iHc: 4.46 kOe. Also, the sintered ferrite magnets of Mn_(0.3)-SrM and [(La-Mn)_(0.3)-SrM exhibited a similar properties to the stoichiometric composition but the coercivity of (La-Mn)_x-SrM was decreased rapidly with x=0.5.
RF Magnetron Sputtering으로 제작된 MnSbPt 합금박막의 자기광학적 성질
송영민(Y. M. Song),이경재(K. J. Lee),김종오(C. O. Kim) 한국자기학회 1996 韓國磁氣學會誌 Vol.6 No.2
The effects of annealing after deposition on the magnetic and magneto-optical properties of MnSbPt thin films prepared by rf sputtering were investigated. The MnSbPt alloy thin films were annealed in a vacuum with 10^(-5) Torr and the air, respectively, as a function of temperature and time. The films annealed at 300℃ for 4 hours was found to have the highest value of the saturation magnetization. The films annealed in the air did not show any thermal degradations, which indicates their chemical stability for the magneto-optical recording process. It was revealed that the Mn₄₃Sb_(46)Pt₁₁ films annealed at 300℃ for 4hours in a vacuum with 10^(-5) Torr exhibit high Kerr rotation angle of 0.8° for the incident wavelength of 550㎚, which is ascribed to the increase of the volume ratio of C1b phase. However, similar to the PtMnSb alloy thin films, these films are still horizontally magnetized and have the coercive field less than 400 Oe.
윤대식,조완식,고은수,이영,박종봉,김종오,Yoon, T.S.,Cho, W.S.,Koo, E.S.,Li, Ying,Park, J.B.,Kim, C.O. 한국재료학회 2001 한국재료학회지 Vol.11 No.1
Nanocrystalline Fe-Sm-O thin films were prepared by RF magnetron reactive sputtering method in $Ar+O_2$mixed atmosphere with the $O_2$content of 5%. The compositions of the thin films were changed by changing the number of $Sm_2O_3$ chips. The best soft magnetic properties of the thin film with the composition of $Fe_{83.4}Sm_{3.4}O_{13.2}$ were saturation flux density of 18 kG, coercivity of 0.82 Oe and effective permeability about 2,600 at 0.5~100 MHz, respectively. The electrical resistivity of Fe-Sm-O thin films was increased with increasing the amount of Sm and O elements which combined each other, the electrical resistivity of$Fe_{83.4}Sm_{3.4}O_{13.2}$ thin film was $130{\mu}{\Omega}cm$. In case of the small amount of Sm and O elements, the microstructures of Fe-Sm-O thin films showed a precipitated phase of $Sm_2O_3$ on the ${\alpha}-Fe$ phase. With the increase of the amount of Sm and O elements, the microstructures of the Fe- Sm-O thin films were changed into a mixed structure of ${\alpha}-Fe$ crystal-phase and Sm-oxide amorphous phase. The Fe-Sm-O thin films with Fe content in the range of 72~94 at% exhibited the quality factor (Q = $\mu$′/$\mu$") of 7~75 up to 50 MHz.
윤대식,조완식,고은수,이영,박종봉,김종오,Yoon, T.S.,Cho, W.S.,Koo, E.S.,Li, Ying,Park, J.B.,Kim, C.O. 한국재료학회 2000 한국재료학회지 Vol.10 No.11
RF magnetron sputtering법으로 초미세결정 Fe-Sm-O계의 박막을 상온에서 제작하여 산소분압에 따른 포화자화, 보자력, 고주파에서의 투자율(100MHz)을 조사하였다. 최적조건인 5%의 산소분압에서 제조한 초미세결정 Fe(sub)83.4Sm(sub)3.4O(sub)13.2박막은 포화자속밀도 18kG, 보자력 0.82 Oe, 실효투자율 (0.5~100MHz) 2,600 이상의 우수한 연자성을 나타내었다. 산소분압이 증가함에 따라 $\alpha$-Fe 결정립의 크기가 감소하여 10%이상의 산소분압에서는 FeO가 생성되어 연자기적 성질이 열화되었다. Fe-Sm-O계 박막의 전기비저항은 산소분압이 증가함에 따라 증가하는 경향을 나타내었으며 우수한 연자기적 성질을 가지는 Fe(sub)83.4Sm(sub)3.4O(sub)13.2박막의 경우, 전기비저항은 130 $\mu$$\Omega$cm이었다. 따라서 미세하게 형성된 $\alpha$-Fe 결정립과 높은 전기비저항 때문에 초미세결정 Fe(sub)83.4Sm(sub)3.4O(sub)13.2박막이 고주파에서 우수한 연자기적 성질을 가지는 것으로 판단된다. The influence of $O_2$partial presure on saturation magnetization, coercivity and effective permeability(0.5~100MHz) of as-deposited Fe-Sm-O thin films, which were fabricated by RF magnetron reactive sputtering method, were investigated. The nanocrystalline Fe(sub)83.4Sm(sub)3.4O(sub)13.2 thin film fabricated at $O_2$partial pressure of 5% exhibits the best magnetic softness with saturation magnetization of 18kG, coercivity of 0.82 Oe and effective permeability about 2,600 at 0.5~100MHz. $\alpha$-Fe grain size is decreased with increasing $O_2$partial pressure. In case of $O_2$partial pressure of 10%, it is observed that FeO compound is formed and soft magnetic properties are decreased. The electrical resistivity of Fe-Sm-O thin films were increased with increasing $O_2$partial pressure, the electrical resistivity of Fe(sub)83.4Sm(sub)3.4O(sub)13.2 thin film with the best soft magnetic properties was 130 $\mu$$\Omega$cm. Therefore, It is assumed that the good soft magnetic properties of Fe(sub)83.4Sm(sub)3.4O(sub)13.2 thin film results from high electrical resistivity and decreasing $\alpha$-Fe grain size due to precipitation of Sm-Oxide phase.
중성자 조사 및 열처리에 따른 SA508 Cl.3강의 자기특성 변화
장기옥(K. O. Chang),김택수(T. S. Kim),심철무(C. M. Sim),지세환(S. H. Chi),김종오(C. O. Kim) 한국자기학회 1998 韓國磁氣學會誌 Vol.8 No.5
In relation to the application of magnetic method to the evaluation of irradiation damage (embrittlement) changes in the magnetic parameters(hysteresis loop and Barkhausen noise) and Vickers microhardness due to neutron irradiation and heat treatment were measured and compared. In the case of irradiation (2.3×10^(19) n/㎠, E≥1 Mev, 288 ℃) hysteresis loop measurements show that susceptibility decreases as coercivity increases. Saturation magnetization do not show any change. Barkhausen noise amplitude and Barkhausen noise energy have decreased while Vickers microhardness has increased. For isothermally heat treated condition of irradiated specimen at 470 ℃ and 540 ℃, Barkhausen noise energy has increased while Vickers microhardness has decreased. Results of BNE and Vickers microhardness are reversed to the results on irradiated condition. All these consistent changes in magnetic parameter and Vickers microhardness measurement, which are thought to be resulted from the interaction between irradiationinduced defects and dislocation, and magnetic domain, respectively, show a possibility that magnetic measurement may be used to the evaluation of material degradation and recovery due to neutron irradiation and heat treatment, respectively, if a relevent large database in prepared.
비정질 Fe - Co - RE - B (RE=Nd, Sm, Gd, Tb) 합금의 자기적 성질
김경섭(K. S. Kim),유성초(S. C. Yu),김창식(C. S. Kim),김종오(J. O. Kim) 한국자기학회 1991 韓國磁氣學會誌 Vol.1 No.2
The temperature-dependent magnetization curves of amorphous Fe-Co-(Nd, Sm, Gd, Tb)-B alloys were measured using a vibrating sample magnetometer from 77 K up to 900 K. The spin wave stiffness constants and the range of the exchange interaction were calculated from the saturation magnetization values at 0 K, Curie temperatures and the Bloch coefficients estimated from the saturation magnetization curves. The low temperature dependence of magnetization is in good agreement with Bloch relation, Ms(T)=Ms(O) (1-BT^(3/2)-CT^(5/2)). The spin wave stiffness constant and the range of exchange interaction are decreased by substitution of heavy rare earth (Tb, Gd).