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First-principles calculations of perpendicular magnetic anisotropy in Fe1-x Co x /MgO(001) thin films.

Cai G, Wu Z, Guo F, Wu Y, Li H, Liu Q, Fu M, Chen T, Kang J - Nanoscale Res Lett (2015)

Bottom Line: As the Co composition increases, the amplitude of PMA increases first from Fe/MgO to Fe12Co4/MgO, and then decreases in Fe10Co6/MgO; finally, the magnetic anisotropy becomes horizontal in Fe8Co8/MgO.Analysis based on the second-order perturbation of the spin-orbit interaction was carried out to illustrate the contributions from Fe and Co atoms to PMA, and the differential charge density was calculated to give an intuitive comparison of 3d orbital occupancy.By adjusting the Co composition in Fe1-x Co x , the density of states of transitional metal atoms will be modulated to optimize PMA for future high-density memory application.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Fujian Key Laboratory of Semiconductor Materials and Applications, Xiamen University, 422 Siming South Road, Xiamen, 361005 People's Republic of China.

ABSTRACT
The perpendicular magnetic anisotropy (PMA) of Fe1-x Co x thin films on MgO(001) was investigated via first-principles density-functional calculations. Four different configurations were considered based on their ground states: Fe/MgO, Fe12Co4/MgO, Fe10Co6/MgO, and Fe8Co8/MgO. As the Co composition increases, the amplitude of PMA increases first from Fe/MgO to Fe12Co4/MgO, and then decreases in Fe10Co6/MgO; finally, the magnetic anisotropy becomes horizontal in Fe8Co8/MgO. Analysis based on the second-order perturbation of the spin-orbit interaction was carried out to illustrate the contributions from Fe and Co atoms to PMA, and the differential charge density was calculated to give an intuitive comparison of 3d orbital occupancy. The enhanced PMA in Fe12Co4/MgO is ascribed to the optimized combination of occupied and unoccupied 3d states around the Fermi energy from both interface Fe and Co atoms, while the weaker PMA in Fe10Co6/MgO is mainly attributed to the modulation of the interface Co-d xy orbital around the Fermi energy. By adjusting the Co composition in Fe1-x Co x , the density of states of transitional metal atoms will be modulated to optimize PMA for future high-density memory application.

No MeSH data available.


Related in: MedlinePlus

Schematics of the calculated structures. (a) Fe/MgO, (b) Fe12Co4/MgO, (c) Fe10Co6/MgO, and (d) Fe8Co8/MgO. Fe, Co, Mg, and O atoms are represented by yellow, blue, green, and red balls, respectively.
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Fig1: Schematics of the calculated structures. (a) Fe/MgO, (b) Fe12Co4/MgO, (c) Fe10Co6/MgO, and (d) Fe8Co8/MgO. Fe, Co, Mg, and O atoms are represented by yellow, blue, green, and red balls, respectively.

Mentions: We performed first-principles density-functional calculations using the Vienna ab initio simulation package (VASP) with the consideration of the spin-orbit interactions. For the electronic exchange-correlation and electron-ion interaction, we adopted the spin-polarized generalized gradient approximation (GGA) [24] and the projector-augmented wave (PAW) potential [25], respectively. A 9 × 9 × 1 k-point mesh was used with the energy cutoff equal to 500 eV. Four 2 × 2 supercells with different Co concentrations were considered in this work: Fe/MgO(001), Fe12Co4/MgO(001), Fe10Co6/MgO(001), and Fe8Co8/MgO(001) (Figure 1). The configurations of FeCo alloys were given as their ground states according to previous work, i.e., L60-Fe12Co4, Fe10Co6, and B2-Fe8Co8 (CsCl type) [26]. Along the z-axis, there were three MgO monolayers, four Fe1−xCox monolayers and 15 Å vacuum. Each supercell includes 40 atoms. The bottom MgO monolayer was fixed as bulk, and the in-plane lattice constant of the supercell was fixed at (cubic MgO: a = 4.212 Å) since a thin ferromagnetic layer was used. All the other layers were fully relaxed until the largest force between the atoms worked out to be less than 1 meV/Å. The magnetic anisotropy energy (MAE) was calculated by taking the difference between the total energy of the magnetization oriented along the in-plane [100] and out-of-plane [001] directions based on the force theorem.Figure 1


First-principles calculations of perpendicular magnetic anisotropy in Fe1-x Co x /MgO(001) thin films.

Cai G, Wu Z, Guo F, Wu Y, Li H, Liu Q, Fu M, Chen T, Kang J - Nanoscale Res Lett (2015)

Schematics of the calculated structures. (a) Fe/MgO, (b) Fe12Co4/MgO, (c) Fe10Co6/MgO, and (d) Fe8Co8/MgO. Fe, Co, Mg, and O atoms are represented by yellow, blue, green, and red balls, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4385311&req=5

Fig1: Schematics of the calculated structures. (a) Fe/MgO, (b) Fe12Co4/MgO, (c) Fe10Co6/MgO, and (d) Fe8Co8/MgO. Fe, Co, Mg, and O atoms are represented by yellow, blue, green, and red balls, respectively.
Mentions: We performed first-principles density-functional calculations using the Vienna ab initio simulation package (VASP) with the consideration of the spin-orbit interactions. For the electronic exchange-correlation and electron-ion interaction, we adopted the spin-polarized generalized gradient approximation (GGA) [24] and the projector-augmented wave (PAW) potential [25], respectively. A 9 × 9 × 1 k-point mesh was used with the energy cutoff equal to 500 eV. Four 2 × 2 supercells with different Co concentrations were considered in this work: Fe/MgO(001), Fe12Co4/MgO(001), Fe10Co6/MgO(001), and Fe8Co8/MgO(001) (Figure 1). The configurations of FeCo alloys were given as their ground states according to previous work, i.e., L60-Fe12Co4, Fe10Co6, and B2-Fe8Co8 (CsCl type) [26]. Along the z-axis, there were three MgO monolayers, four Fe1−xCox monolayers and 15 Å vacuum. Each supercell includes 40 atoms. The bottom MgO monolayer was fixed as bulk, and the in-plane lattice constant of the supercell was fixed at (cubic MgO: a = 4.212 Å) since a thin ferromagnetic layer was used. All the other layers were fully relaxed until the largest force between the atoms worked out to be less than 1 meV/Å. The magnetic anisotropy energy (MAE) was calculated by taking the difference between the total energy of the magnetization oriented along the in-plane [100] and out-of-plane [001] directions based on the force theorem.Figure 1

Bottom Line: As the Co composition increases, the amplitude of PMA increases first from Fe/MgO to Fe12Co4/MgO, and then decreases in Fe10Co6/MgO; finally, the magnetic anisotropy becomes horizontal in Fe8Co8/MgO.Analysis based on the second-order perturbation of the spin-orbit interaction was carried out to illustrate the contributions from Fe and Co atoms to PMA, and the differential charge density was calculated to give an intuitive comparison of 3d orbital occupancy.By adjusting the Co composition in Fe1-x Co x , the density of states of transitional metal atoms will be modulated to optimize PMA for future high-density memory application.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Fujian Key Laboratory of Semiconductor Materials and Applications, Xiamen University, 422 Siming South Road, Xiamen, 361005 People's Republic of China.

ABSTRACT
The perpendicular magnetic anisotropy (PMA) of Fe1-x Co x thin films on MgO(001) was investigated via first-principles density-functional calculations. Four different configurations were considered based on their ground states: Fe/MgO, Fe12Co4/MgO, Fe10Co6/MgO, and Fe8Co8/MgO. As the Co composition increases, the amplitude of PMA increases first from Fe/MgO to Fe12Co4/MgO, and then decreases in Fe10Co6/MgO; finally, the magnetic anisotropy becomes horizontal in Fe8Co8/MgO. Analysis based on the second-order perturbation of the spin-orbit interaction was carried out to illustrate the contributions from Fe and Co atoms to PMA, and the differential charge density was calculated to give an intuitive comparison of 3d orbital occupancy. The enhanced PMA in Fe12Co4/MgO is ascribed to the optimized combination of occupied and unoccupied 3d states around the Fermi energy from both interface Fe and Co atoms, while the weaker PMA in Fe10Co6/MgO is mainly attributed to the modulation of the interface Co-d xy orbital around the Fermi energy. By adjusting the Co composition in Fe1-x Co x , the density of states of transitional metal atoms will be modulated to optimize PMA for future high-density memory application.

No MeSH data available.


Related in: MedlinePlus