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고체내의 전자빔 산란에 대한 몬테카를로 시뮬레이션 연구
이철의(Cheol Eui Lee),이규원(kyu Won Lee),윤성민(Sung Min Yoon) 한국생산제조학회 2007 한국공작기계학회 춘계학술대회논문집 Vol.2007 No.-
고체 내에 입사된 전자빔의 산란 과정을 몬테카를로 방법으로 시뮬레이션 했다. 탄성 산란에 대해서는 screened Rutherford 산란 단면적을 사용했고 비탄성 산란에 대해서는 Gryzinsky의 산란 단면적이 사용되었다. 산란 전자의 좌표계와 실험실 좌표계 사이에 회전변환을 도입하여 계산 결과의 정밀도와 효율성을 개선했다. 입사된 전자의 산란 전후 위치와 에너지를 계산하여 전자빔의 침투거리에 따른 전자빔의 넓어짐과 에너지 감소를 계산하였다.
Nonmagnetic Impurity Effect in CuF₂ㆍ 2H₂O
이창훈(Chang Hoon Lee),이철의(Cheol Eui Lee) 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.2
We have measured the magnetic susceptibilities of a CuF₂ㆍ 2H₂O sample by means of the SQUID (superconducting quantum interference device) at the magnetic fields of 0.5 T and 1 mT, in the temperature range 5-300 K. The sample was found to contain some nonmagnetic calcium and magnesium impurities by the elemental analysis. Our measurements differ from known results for pure CuF₂ㆍ 2H₂O and are well explained by the effect of the nonmagnetic impurities in our sample. The purity of our sample derived from the temperature dependence of the susceptibilities was compared with that from the elemental analysis.
63CU NQR Study of the Anisotropy in YBa₂Cu₃O7
장비(B. Chang),이철의(Cheol Eui Lee) 한국자기학회 1994 韓國磁氣學會誌 Vol.4 No.1
We have studied the room temperature anisotropy in the high Tc superconductor YBa₂Cu₃O_7 by means of the (63)^Cu nuclear quadrupole resonance (NQR). For the magnetically oriented powder samples, NQR signals were obtained only when the RF magnetic field is applied perpendicular to the direction of the crystalline c-axis. Significant differences in the spin~lattice relaxation times (T₁) and the lineshapes were observed between the unoriented powder sample and the magnetically oriented sample.
S.H.Kim,이철의,K.W.Lee,Cheol Eui Lee,강원,홍관수 한국물리학회 2004 Current Applied Physics Vol.4 No.5
Molecular motions in an organic superconductor, (TMTSF)2PF6, were investigated by means of19F NMR. The temperature dependence of the spinlattice relaxation rate was tted with two distinct molecular motions, indicating two dierent modes ascribedto the distorted octahedral anion sublattice. As a result, anisotropic anionic motions, which may trigger the subtle mesoscopic electronic instability in this quasi-1D conductor, were revealed.
Nuclear Magnetic Relaxation in Anisotropic Heisenberg Antiferromagnet MnCl₂ㆍ4H₂O
이창훈(Chang Hoon Lee),이철의(Cheol Eui Lee) 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.1
We have studied the room temperature ¹H nuclear magnetic relaxation in anisotropic antiferromagnet MnCl₂ㆍ4H₂O using a wide range of ¹H NMR (nuclear magnetic resonance) field. Being a system of dense paramagnetic Mn++ ions at room temperature, MnCl₂ㆍ4H₂O shows some features that can be expected from dilute paramagnetic systems, as well as some results that drastically deviate from the dilute paramagnetic approximations. Besides, ¹H nuclei exhibit an anomalous deviation in the spin-lattice relaxation time (T₁) around the field of 0.7 T.
Superexchange in the Dense Paramagnet CuF₂
김준형(Jun Hyeong Kim),이창훈(Chang Hoon Lee),이철의(Cheol Eui Lee) 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.3
We have studied the paramagnetic CuF₂ using the techniques of pulsed nuclear magnetic resonance (NMR). The powder sample revealed two well-separated lines from the distinct (19)^F sites at room temperature and at 77 K. The distinct frequency shifts of the two lines appear to arise from electron transfers. Furthermore, the two sites have very short spin-lattice relaxation times (T₁). The frequency-shifted site has the shorter T₁ than the unshifted one, reflecting the difference of the electron environments of the two sites.