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Effect of Gd doping and O deficiency on the Curie temperature of EuO.

Jutong N, Eckern U, Mairoser T, Schwingenschlögl U - Sci Rep (2015)

Bottom Line: The effect of Gd doping and O deficiency on the electronic structure, exchange interaction, and Curie temperature of EuO in the cubic and tetragonal phases is studied by means of density functional theory.For both defects, the Curie temperature is found to exhibit a distinct maximum as a function of the defect concentration.The existence of optimal defect concentrations is explained by the interplay of the on-site, RKKY, and superexchange contributions to the magnetism.

View Article: PubMed Central - PubMed

Affiliation: Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany.

ABSTRACT
The effect of Gd doping and O deficiency on the electronic structure, exchange interaction, and Curie temperature of EuO in the cubic and tetragonal phases is studied by means of density functional theory. For both defects, the Curie temperature is found to exhibit a distinct maximum as a function of the defect concentration. The existence of optimal defect concentrations is explained by the interplay of the on-site, RKKY, and superexchange contributions to the magnetism.

No MeSH data available.


Exchange interaction and corresponding TC as a function of the O vacancy concentration for the cubic phase ((a1), (b1)) and the tetragonal phase ((a2), (b2)).
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f5: Exchange interaction and corresponding TC as a function of the O vacancy concentration for the cubic phase ((a1), (b1)) and the tetragonal phase ((a2), (b2)).

Mentions: We next analyze the effects of O deficiency by means of the DOS projected on the Eu 4f, 5d and O 2p orbitals, see Fig. 4, for different O vacancy concentrations. In addition, Fig. 5 addresses the dependences of the different exchange terms and of TC on the O vacancy concentration. As expected, O deficiency in EuO causes almost rigid shifts of all states to lower energy, giving rise to the well known metal-insulator transition. With increasing O deficiency more and more of the charge donated by the O vacancies occupies the Eu 5d conduction bands. It is generally accepted that positive effects on TC due to O deficiency originate from this extra charge populating the conduction band, and giving rise to enhanced RKKY exchange1254344, which corresponds to an increase in J1. However, also the gap between the majority spin Eu 5d and 4f states decreases substantially, and the f-d hopping is enhanced correspondingly, see Fig. 5(a1). The band structure (not shown) demonstrates that the exchange splitting of the Eu 5d states at the conduction band edge is reduced significantly for 6.25% O vacancy concentration, as compared to the pristine case, and further slightly decreases for higher O vacancy concentrations.


Effect of Gd doping and O deficiency on the Curie temperature of EuO.

Jutong N, Eckern U, Mairoser T, Schwingenschlögl U - Sci Rep (2015)

Exchange interaction and corresponding TC as a function of the O vacancy concentration for the cubic phase ((a1), (b1)) and the tetragonal phase ((a2), (b2)).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4306962&req=5

f5: Exchange interaction and corresponding TC as a function of the O vacancy concentration for the cubic phase ((a1), (b1)) and the tetragonal phase ((a2), (b2)).
Mentions: We next analyze the effects of O deficiency by means of the DOS projected on the Eu 4f, 5d and O 2p orbitals, see Fig. 4, for different O vacancy concentrations. In addition, Fig. 5 addresses the dependences of the different exchange terms and of TC on the O vacancy concentration. As expected, O deficiency in EuO causes almost rigid shifts of all states to lower energy, giving rise to the well known metal-insulator transition. With increasing O deficiency more and more of the charge donated by the O vacancies occupies the Eu 5d conduction bands. It is generally accepted that positive effects on TC due to O deficiency originate from this extra charge populating the conduction band, and giving rise to enhanced RKKY exchange1254344, which corresponds to an increase in J1. However, also the gap between the majority spin Eu 5d and 4f states decreases substantially, and the f-d hopping is enhanced correspondingly, see Fig. 5(a1). The band structure (not shown) demonstrates that the exchange splitting of the Eu 5d states at the conduction band edge is reduced significantly for 6.25% O vacancy concentration, as compared to the pristine case, and further slightly decreases for higher O vacancy concentrations.

Bottom Line: The effect of Gd doping and O deficiency on the electronic structure, exchange interaction, and Curie temperature of EuO in the cubic and tetragonal phases is studied by means of density functional theory.For both defects, the Curie temperature is found to exhibit a distinct maximum as a function of the defect concentration.The existence of optimal defect concentrations is explained by the interplay of the on-site, RKKY, and superexchange contributions to the magnetism.

View Article: PubMed Central - PubMed

Affiliation: Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany.

ABSTRACT
The effect of Gd doping and O deficiency on the electronic structure, exchange interaction, and Curie temperature of EuO in the cubic and tetragonal phases is studied by means of density functional theory. For both defects, the Curie temperature is found to exhibit a distinct maximum as a function of the defect concentration. The existence of optimal defect concentrations is explained by the interplay of the on-site, RKKY, and superexchange contributions to the magnetism.

No MeSH data available.