Doping-induced metallicity and coexistence of magnetic subsystems in K2Fe4+xSe5

TitleDoping-induced metallicity and coexistence of magnetic subsystems in K2Fe4+xSe5
Publication TypeJournal Article
Year of Publication2012
AuthorsKe LQ, van Schilfgaarde M, Antropov V
Journal TitleSolid State Communications
Date Published10
Type of ArticleArticle
ISBN Number0038-1098
Accession NumberWOS:000308841300012
Keywordscs, Exchange coupling, Frustrations, KFe2Se2, Nesting, superconductivity

Electronic structure calculations are used to analyze the electronic and magnetic properties in K2Fe4+xSe5. Fe atoms can be divided into two distinct groups. The x=0 (parent) compound forms an insulating, collinear, local moment phase with high Neel temperature. We show that large biquadratic exchange coupling and exchange-elastic interactions stabilize the magnetic order. For x > 0 the additional Fe atoms fill vacancy sites. They form impurity bands for small x, which broaden as x increases. They determine the states at the Fermi level and may be viewed as a magnetic subsystem separate from the host. Spin fluctuations are prevalent because magnetic interactions between the 'defect' and the 'parent' atoms are relatively weak, while chemical fluctuations are prevalent for low x. Fluctuations of either type lead to the formation of a weakly metallic state. The unusual coexistence of the two magnetic subsystems offers a new perspective as to how superconductivity and strong antiferromagnetism can coexist. We argue that spin fluctuations of the impurity subsystem share common features with the Fe-pnictide superconductors. Published by Elsevier Ltd.

URL<Go to ISI>://WOS:000308841300012
Alternate JournalSolid State Commun.