Improvement of the strength is one of the most important subjects on soft magnetic composite (SMC) to increase the applica ble items. In this study, lubricants for inner lubricating SMC, which can be produced in lower cost than die wall-lubricatin g SMC, varied to investigate their effect on the strength. The newly developed SMC with self-lubricating resin shows high st rength equivalent to that of SMC obtained by die wall lubrication.

Recently, there has been a growing demand for soft magnetic materials with high conversion characteristics, due to the trend of electric devices to higher-frequency range. For ruduceing core loss in the high-frequency range, using finely grained and high-resistivity Fe-based alloy powder is most efficient methods. But, conventionally, there's been a compressibility problem for such powder. In this work, Fe-based alloy powder that offers both high resistivity and high compressibility was developed by studyuing composition of the powder, and reduction of core loss of P/M soft magnetic materials in the high frequency range was achieved.

Metal powder for dust core application was developed. The powder can be produced improved high-pressure water atomization process. The process has produced powder of spherical shape and lower coercivity. The dust core obta ined shows lower core loss.

The magnetic inductance of nanocrystalline Fe73Si16B7Nb3Cu1 and an amorphous FeSiB powder sheet has been investigated to identify RFID performance. The powder was mixed with binder and solvent and tape-casted to form films. Results show annealing significantly influenced on the inductance of the material. The surface oxidation of the particles was the main reason for the reduced inductance. The maximum inductance of Fe73Si16B7Nb3Cu1 alloy was about 88μH at 17.4 MHz, about 65% greater compared to the FeSiB alloy. The higher inductance in the nanocrystalline alloy indicates it may be used as a potential replacement of current RFID materials.

Co-based amorphous powder was produced by a new atomization process “Spinning Water Atomization Process (SWAP)”, having rapid super-cooling rate. The composition of the alloys was ((Co0.95Fe0.05)1-xCrx)75Si15B10 (x=0, 0.025, 0.05, 0.075). The powders became the amorphous state even if particle size was up to about 500 μm. The coercive force of powders was about 0.35 - 0.7 Oe. Furthermore, Co-based amorphous powder cores with glass binders were made by cold-pressing and sintering methods. The initial permeability of the core in the frequency range up to 100 kHz was about 110, and the core loss at 100 kHz for Bm = 0.1 T was 350 kW/m3.

The amorphous alloy strip was pulverized to get a flake-shaped powder after annealing at for 90 min and subsequently ground to obtain finer flake-shaped powder by using a ball mill. The powder was mixed with polyimide-based binder of , and then the mixture was cold compacted to make a toroidal powder core. After crystallization treatment for 1 hour at , the powder was transformed from amorphous to nanocrystalline with the grain size of . Soft magnetic characteristics of the powder core was optimized at with the insulating binder of 3wt%. As a result, the powder core showed the outstanding magnetic properties in terms of core loss and permeability, which were originated from the optimization of the grain size and distribution of the insulating binder.

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 α-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 μΩcm이었다. 따라서 미세하게 형성된 α-Fe 결정립과 높은 전기비저항 때문에 초미세결정 Fe(sub)83.4Sm(sub)3.4O(sub)13.2박막이 고주파에서 우수한 연자기적 성질을 가지는 것으로 판단된다.

RF magnetron reactive sputtering법으로 Fe75.5Zr8.3N16.2/SiO2(250Å) 다층 박막을 FeZrN의 두께를 변화시키면서 제조하고, 제조된 박막을 진공 열처리하여 열처리 온도에 따른 포화자화, 보자력, 고주파에서의 투자율 그리고 열적 안정성을 조사하였다. Fe75.5Zr8.3N16.2/SiO2(250Å) 다층박막은 FeZrN의 두께가 800Å이상일 때 좋은 연자성을 나타내었다. Fe75.5Zr8.3N16.2/SiO2(250Å)다층 박막을 450˚C로 열처리 했을 때 포화자속밀도(1.08 T), 보자력 0.41 Oe, 1 MHz에서의 실효 투자율은 3000이상의 연자성을 나타내었다. 그 이유는 X-선 회절 분석 결과 열처리에 의해서 ZrN 미결정이 석출하여 α-Fe 결정 성장이 억제되어 우수한 연자기적 성질이 나타난다고 판단된다. 이때 α-Fe 입자 크기는 40-50Å, ZrN의 입자 크기는 10-15Å이다. 그리고 실효 투자율의 주파수 의존성에서 단층막에서는 5 MHz 이상에서 실효 투자율이 급격히 감소하는 경향을 보였으나, 다층막에서는 40MHz까지 실효 투자율이 1600이 되어 고주파에서의 연자성이 개선되었다.

자기기록의 고밀도화로 인해 보자력(Hc)이 큰 자기기록매체가 필요하게 되었다. 고보자력매체에 신호를 충분히 기록하기 위해서는 보다 강한 자장이 필요하다. 이 때문에 포화자화(Ms)가 큰 재료가 필요하며 고주파 영역에서 실효투자율(μeff)이 높아야 한다. Fe계 합금박막은 이에 적합한 재료이다. 본 연구에서는 Fe의 결정자기이방성에 영향을 미치는 Si과 Fe의 격자 변형을 유도할 수 있는 B를 첨가하였다. Fe-B-Si 계 박막을 질소분위기 중에서 RF Matnetron Sputter로 제작하여 연자기적 특성에 관하여 고찰하였다. Fe91.49B4.01Si4.50at% 박막은 350˚C에서 1시간 열처리를 행함으로써 약 900(10MHz) 정도의 투자율과 7.6Oe의 보자력을 나타냈으며 포화자화는 1300emu/㎤를 얻었다.

RF & DC magnetron sputtering장치를 이용하여 Ar과 Ar+N2혼합가스분위기에서 Fe/Co및 Fe-N/Co-N다층막을 각각 제조하였다. 제작된 다층막을 100˚C ~ 500˚C로 각각 1시간씩 열처리하였다. Fe막의 두께와 열처리 온도에 따른 Fe/Co다층막의 포화자화와 보자력을 측정하고, 투자율을 조사하였다. Fe/Co(70Å/15Å)다층막에서 포화자화는 1.8Oe이다. 보자력은 열처리 온도 250˚C까지는 일정한 값(1.8Oe)을 가지나. 250˚C ~ 300˚C에서는 약간 증가하고, 300˚C이상에서는 갑자기 증가한다. 질소 유량비(N2/Ar+N2)가 4%인 조건에서 제작한 Fe-N/Co-N 다층박막의 보자력은 5Oe이고, 열처리 온도가 증가함에 따라 감소하다가 250˚C에서 최소값, 2Oe를 나타내고 그 이상의 온도에서 급격히 증가한다.

We use the outer gap model to explain the spectrum and the energy dependent light curves of the X-ray and soft γ-rayradiations of the spin-down powered pulsar PSR B1509-58. In the outer gap model, most pairs inside the gap are createdaround the null charge surface and the gap’s electric field separates the opposite charges to move in opposite directions.Consequently, the region from the null charge surface to the light cylinder is dominated by the outflow current and that fromthe null charge surface to the star is dominated by the inflow current. We suggest that the viewing angle of PSR B1509-58 onlyreceives the inflow radiation. The incoming curvature photons are converted to pairs by the strong magnetic field of the star.The X-rays and soft γ-rays of PSR B1509-58 result from the synchrotron radiation of these pairs. The magnetic pair creationrequires a large pitch angle, which makes the pulse profile of the synchrotron radiation distinct from that of the curvatureradiation. We carefully trace the pulse profiles of the synchrotron radiation with different pitch angles. We find that thedifferences between the light curves of different energy bands are due to the different pitch angles of the secondary pairs, andthe second peak appearing at E > 10 MeV comes from the region near the star, where the stronger magnetic field allows thepair creation to happen with a smaller pitch angle.