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Y대신 Na을 치환한 Y-123 고온 초전도체의 강한 상자성
남균(Kyun Nahm),이경복(Kyeong Bock Lee),박춘만(Choon Mahn Park),김철구(Chul Koo Kim) 한국자기학회 1991 한국자기학회 학술연구발표회 논문개요집 Vol.1 No.1
고온 초전도에 Y-123에서 Y 대신 Na를 치환한 시료를 제작하여 자기적인 측정과 x-ray 분석을 하였다. 자기적 측정에서 강한 상자성 moment가 관측되는 것은 BaCuO₂상의 존재때문임이 밝혀졌다. BaCuO₂의 양은 Na 양에 비례하여 증가하므로 자기적 moment가 Na양에 비례하는 것과 같이 보인다.
남균(Kyun Nahm),유상구(Sang Koo You),김철구(Chul Koo Kim) 한국자기학회 2005 韓國磁氣學會誌 Vol.15 No.5
The elastic constants, C', of Th₃P₄-type structure compounds, La₃S₄ and Ce₃S₄, have been analyzed on the basis of band Jahn Teller mechanism. The distinct difference between two compounds lies in the fact that Ce³+ ion has a f electron which produces magnetism. It is shown that the band Jahn-Teller effect is sensitively influenced by the energy splitting of f electronic bands by a cubic crystal field in Ce₃S₄, and f electrons suppress the elastic softening effect. The energy splitting value obtained from the calculation of elastic constants is found to agree well with the experimental value obtained from the magnetic susceptibility measurement.
차정원(Jung Won Cha),남균(Kyun Nahm),김철구(Chul Koo Kim) 한국자기학회 2007 韓國磁氣學會誌 Vol.17 No.3
The single crystal Nd₃Se₄ with the bcc-Th₃P₄ type structure is grown and the temperature dependent magnetic susceptibilities are measured between 4 K and 300 K. The experimental data are compared with the theoretically calculated susceptibilities which depend on the splitting energies of the Nd³? ground state under the crystal field effect. We find that the magnetic susceptibility of the ion in Nd₃Se₄ is not affected by the crystal field effect. The spontaneous magnetization curve below T<SUB>c</SUB>= 53K of Nd₃Se₄ corresponds to the Brillouin function of Nd₃Se₄ with J = 9/2.
단결정 MnF₂(1.5 % EuF₃)의 Photoluminescence
권순혁(Soon Hyuk Kwon),남균(Kyun Nahm),김철구(Chul Koo Kim) 한국자기학회 2007 韓國磁氣學會誌 Vol.17 No.1
The IR (Infra-Red) spectrum and PL(Photoluminescence) of the antiferromagnetic pure MnF₂ and the single crystal MnF₂ (1.5 % EuF₃) with the rutile structures were measured. The detailed analysis of the measured PL data showed the differences of the optical property between the single crystal MnF₂ (1.5% EuF₃) and the pure MnF₂. It was found that the additional PL peak by the doping of the EuF₃ in MnF₂ is originated from the f-d transition of Eu<SUP>3+</SUP> from the temperature dependent intensity measurement.
이준영(Jun Young Lee),남균(Kyun Nahm),김철구(Chul Koo Kim) 한국자기학회 2006 韓國磁氣學會誌 Vol.16 No.5
In order to investigate the magnetic properties of Eu ions in the single crystal MnF₂, the temperature dependent magnetic susceptibilities of the antiferromagnetic MnF₂ and the single crystal MnF₂(1.5 % EuF₃) with the rutile structures were measured in the temperature range from 4 K to 300 K. The detailed analysis of the measured susceptibilities showed that the magnetic susceptibility by the doping of the small amount EuF₃ in the antiferromagnetic single crystal MnF₂ follows the antiferromagnetic Curie-Weiss law with the negative paramagnetic Curie temperature similarly as in MnF₂. It was also found that Eu ion has +3 valence. This solves the long standing discrepancy on this problem.
우상욱(Sang Wook Wu),노현식(Hyeon Sig Noh),남균(Kyun Nahm),김철구(Chul Koo Kim),권태송(Tae Song Kwon) 한국자기학회 1992 한국자기학회 학술연구발표회 논문개요집 Vol.2 No.2
좁고 이중으로 겹쳐진 띠 구조를 갖는 반 강자성 물질의 탄성성질을 설명하기 위해, Model Hamiltonian으로 Hubbard Hamiltonian을 사용하고, Gorkov’s decomposition 방법과 RPA (Random phase Approximation)근사를 사용하였다. 그 결과, Antiferromagnetism이 interband transition항으로부터 유도되었고, Model Hamiltonian을 diagonalize시켜 Energy eigenvalue와 eigenfunction을 구했다. 이제, 반강자성으로 상전이된 상태에 tetragonal type - strain을 걸고, 탄성상수를 계산하고 결과와 비교해 보았다.
김철구(Chul Koo Kim),권태송(Tae Song Kwon),남균(Kyun Nahm) 한국자기학회 1991 한국자기학회 학술연구발표회 논문개요집 Vol.1 No.1
자성 물질의 탄성계수의 온도 의존성을 설명하는 이론을 체계적으로 제시하였으며, 이 이론을 지금까지 적용되지 않은 다른 형태의 자기적인 물질에 적용시키는 문제에 대해서도 논의하였다.