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Insulator–metal transition driven by pressure and B‐site disorder in double perovskite La 2 CoMnO 6
Author(s) -
Lv Shuhui,
Liu Xiaojuan,
Li Hongping,
Han Lin,
Wang Zhongchang,
Meng Jian
Publication year - 2012
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.22976
Subject(s) - ionic radius , condensed matter physics , curie temperature , ground state , spin states , ferromagnetism , ionic bonding , chemistry , spin transition , materials science , ion , physics , atomic physics , organic chemistry
The ground state of double perovskite oxide La 2 CoMnO 6 (LCMO) and how it is influenced by external pressure and antisite disorder are investigated systematically by first‐principles calculations. We find, on the consideration of both the electron correlation and spin–orbital coupling effect, that the LCMO takes on insulating nature, yet is transformed to half metallicity once the external pressure is introduced. Such tuning is accompanied by a spin‐state transition of Co 2+ from the high‐spin state (t 5 2g e 2 g ) to low‐spin state (t 6 2g e 1 g ) because of the enhancement of crystal‐field splitting under pressure. Using mean‐field approximation theory, Curie temperature of LCMO with Co 2+ being in low‐spin state is predicted to be higher than that in high‐spin state, which is attributed to the enhanced ferromagnetic double exchange interaction arising from the shrinkage of CoO and MnO bonds as well as to the increase in bond angle of CoOMn under pressure. We also find that antisite disorder in LCMO enables such transition from insulating to half‐metallic state as well, which is associated with the spin‐state transition of antisite Co from high to low state. It is proposed that the substitution of La 3+ for the rare‐earth (RE) ions with smaller ionic radii could open up an avenue to induce a spin‐state transition of Co, rendering thereby the RE 2 CoMnO 6 a promising half‐metallic material. © 2012 Wiley Periodicals, Inc.