제일원리 전자구조 계산을 이용한 FCC 결정구조를 가지는 C60Hn의 자성에 관한 연구

Abstract

최근의 제일원리 밀도 범함수 이론계산 연구[K. W. Lee and C. E. Lee Phys. Rev. Lett. 106 166402 (2011)]는 FCC 결정구조를 가지는 C60 결정에 수소가 홀 수개 흡착하였을 때 itinerant band model에 의해 stoner ferromagnetism이 존재함을 제안하였다. 하지만, 우리의 범함수 이론계산은 FCC C60Hn(n=홀수)에서 반자성 상태가 강자성 상태보다 약간 더 안정됨을 보인다. 강자성 상태보다 반강자성 상태가 더 안정되는 이러한 경향성은 dimer (C60H)2 분자에서도 유사한데, 각 C60H가 intramolecular exchange에 의해 스핀 분극화되고 각 C60H의 두개의 자기모멘트는 반강자성으로 정렬된다. 이러한 결과는 FCC C60Hn(n=홀수)에서 반강자성 현상의 메커니즘이 H dopants에 의해 생긴 자기 모멘트들 사이의 반강자성 superexchange interaction과 연관됨을 증명한다.| A recent density-functional calculation for fcc C60Hn (n = odd) [K.W. Lee and C. E. Lee, Phys. Rev. Lett. 106, 166402 (2011)] proposed the existence of Stoner ferromagnetism based on an itinerant band model. However, our density-functional calculation shows that the antiferromagnetic (AFM) configuration is slightly more stable than the ferromagnetic (FM) one. This preference for antiferromagnetism over ferromagnetism is analogous to the case of a dimer (C60H)2, where each C60H is spin polarized by an intramolecular exchange and the two magnetic moments are antiferromagnetically coupled with each other. The results demonstrate that the underlying mechanism of the magnetic order in fcc C60Hn is associated with the AFM superexchange between the magnetic moments created by H dopants.; A recent density-functional calculation for fcc C60Hn (n = odd) [K.W. Lee and C. E. Lee, Phys. Rev. Lett. 106, 166402 (2011)] proposed the existence of Stoner ferromagnetism based on an itinerant band model. However, our density-functional calculation shows that the antiferromagnetic (AFM) configuration is slightly more stable than the ferromagnetic (FM) one. This preference for antiferromagnetism over ferromagnetism is analogous to the case of a dimer (C60H)2, where each C60H is spin polarized by an intramolecular exchange and the two magnetic moments are antiferromagnetically coupled with each other. The results demonstrate that the underlying mechanism of the magnetic order in fcc C60Hn is associated with the AFM superexchange between the magnetic moments created by H dopants.