Publikationsdatum:
2016-06-23
Beschreibung:
Activating ferromagnetic couplings of transition-metallic ions in the antiferromagnetic metal oxide semiconductors is desired for creating ferromagnetic semiconductors for spintronics applications. Here, we report intrinsic ferromagnetic coupling in a typical antiferromagnetic metal oxide Co 3 O 4 , by virtue of a hybrid structure that modifies the valence state of Co ions. The Co 3 O 4 quantum dots exhibit ferromagnetism of 2.2 emu/g at 2 K after hybridization with reduced graphene oxide (RGO). In this hybrid structure, electron-transfer from RGO to Co 3 O 4 occurs and Co 3+ ions occupying the octahedral (O h ) positions are converted into Co 2+ . Then the super-exchange interactions between Co 2+ ions at T d (tetrahedral) and O h positions switch the magnetic coupling of Co 2+ ( T d )–Co 2+ ( T d ) from antiferromagnetic to ferromagnetic. These results offer promise for tailoring the spin exchange interactions of oxide semiconductors for spintronics applications.
Print ISSN:
0003-6951
Digitale ISSN:
1077-3118
Thema:
Physik
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