2010年3月
Theory of room temperature ferromagnet V(TCNE)x (1:5 < x < 2): Role of hidden flat bands
Journal of the Physical Society of Japan
- ,
- ,
- 巻
- 79
- 号
- 3
- 記述言語
- 英語
- 掲載種別
- DOI
- 10.1143/JPSJ.79.034712
Theoretical studies on the possible origin of room temperature ferromagnetism (ferromagnetic once crystallized) in the molecular transition metal complex, V(TCNE)x (1:5 <
x <
2) have been carried out. For this family, there have been no definite understanding of crystal structure so far because of sample quality, though the effective valence of V is known to be close to +2. Proposing a new crystal structure for the stoichiometric case of x = 2, where the valence of each TCNE molecule is -1 and resistivity shows insulating behavior, exchange interaction among d-electrons on adjacent V atoms has been estimated based on the cluster with 3 vanadium atoms and one TCNE molecule. It turns out that Hund's coupling among d orbitals within the same V atoms and antiferromagnetic coupling between d oribitals and LUMO of TCNE (bridging V atoms) due to hybridization result in overall ferromagnetism (to be precise, ferrimagnetism). This view based on localized electrons is supplemented by the band picture, which indicates the existence of a flat band expected to lead to ferromagnetism as well consistent with the localized view. The off-stoichiometric cases (x <
2), which still show ferromagnetism but semiconducting transport properties, have been analyzed as due to Anderson localization. © 2010 The Physical Society of Japan.
x <
2) have been carried out. For this family, there have been no definite understanding of crystal structure so far because of sample quality, though the effective valence of V is known to be close to +2. Proposing a new crystal structure for the stoichiometric case of x = 2, where the valence of each TCNE molecule is -1 and resistivity shows insulating behavior, exchange interaction among d-electrons on adjacent V atoms has been estimated based on the cluster with 3 vanadium atoms and one TCNE molecule. It turns out that Hund's coupling among d orbitals within the same V atoms and antiferromagnetic coupling between d oribitals and LUMO of TCNE (bridging V atoms) due to hybridization result in overall ferromagnetism (to be precise, ferrimagnetism). This view based on localized electrons is supplemented by the band picture, which indicates the existence of a flat band expected to lead to ferromagnetism as well consistent with the localized view. The off-stoichiometric cases (x <
2), which still show ferromagnetism but semiconducting transport properties, have been analyzed as due to Anderson localization. © 2010 The Physical Society of Japan.
- ID情報
-
- DOI : 10.1143/JPSJ.79.034712
- ISSN : 0031-9015
- ISSN : 1347-4073
- SCOPUS ID : 77949743400