Ju n 20 01 Spin state and phase competition in TbBaCo 2 O 5 . 5 and the lanthanide series
نویسنده
چکیده
A clear physics picture of TbBaCo2O5.5 is revealed on the basis of density functional theory calculations. An antiferromagnetic (AFM) superexchange coupling between the almost high-spin Co ions competes with a ferromagnetic (FM) interaction mediated by both p-d exchange and double exchange, being responsible for the observed AFM-FM transition. And the metal-insulator transition is accompanied by an xy/xz orbital-ordering transition. Moreover, this picture can be generalized to the whole lanthanide series, and it is predicted that a few room-temperature magnetoresistance materials could be found in LnBa1−xAxCo2O5+δ (Ln=Ho,Er,Tm,Yb,Lu; A=Sr,Ca,Mg).
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