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要旨:
Using first-principles density-functional theory, we have investigated
the electronic and magnetic properties of recently synthesized and
characterized 5d double-perovskites Sr2BOsO6(B = Y, In, Sc). The
electronic structure calculations show that in all compounds the Os5+
(5d(3)) site is the only magnetically active one, whereas Y3+, In3+, and
Sc3+ remain in nonmagnetic states with Sc/Y and In featuring d(0) and
d(10) electronic configurations, respectively. Our studies reveal the
important role of closed-shell (d(10)) versus open-shell (d(0))
electronic configurations of the nonmagnetic sites in determining the
overall magnetic exchange interactions. Although the magnetic Os5+
(5d(3)) site is the same in all compounds, the magnetic superexchange
interactions mediated by nonmagnetic Y/In/Sc species are strongest for
Sr2ScOsO6, weakest for Sr2InOsO6, and intermediate in the case of the Y
(d(0)) due to different energy overlaps between Os-5d and Y/In/Sc-d
states. This explains the experimentally observed substantial
differences in the magnetic transition temperatures of these materials,
despite an identical magnetic site and underlying magnetic ground state.
Furthermore, short-range Os-Os exchange interactions are more prominent
than long-range Os-Os interactions in these compounds, which contrasts
with the behavior of other 3d-5d double perovskites.
