2001/08/30 by G. Baskaran
Physics and Astronomy · #Physics of Superconductivity and Magnetism #Rare-earth and actinide compounds #Superconductivity in MgB2 and Alloys #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.65.212403
published as Physical Review, B65, 212403 (2002) · 4 pages, 2 figures; minor corrections, references added
arxiv created 2001/08/30 · openalex publication_date 2002/05/16 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Doped divalent hexaborides such as Sr_1\ensuremath-xLaxB6 exhibit a high Tc ferromagnetism. We isolate a degenerate pair of 2p orbitals of boron with two valence electrons, invoke electron correlation and Hund coupling, to suggest that the undoped state is better viewed as a spin-1 Mott insulator; it is predicted to be a type of 3d Haldane gap phase with a spin gap \ensuremath∼0.1eV, much smaller than the charge gap of >1.0eV seen in angle-resolved photoemission spectroscopy. The experimentally seen high Tc ``ferromagnetism'' is argued to be a complex magnetic order in disguise---either a canted six-sublattice antiferromagnetic (\ensuremath≈120\ifmmode^∘\else\textdegree\fi) order or its quantum melted version, a chiral spin liquid state, arising from a type of double-exchange mechanism.