Limits...
Electronic and magnetic properties of SnO2/CrO2 thin superlattices.

Borges PD, Scolfaro LM, Leite Alves HW, da Silva EF, Assali LV - Nanoscale Res Lett (2011)

Bottom Line: In this article, using first-principles electronic structure calculations within the spin density functional theory, alternated magnetic and non-magnetic layers of rutile-CrO2 and rutile-SnO2 respectively, in a (CrO2)n(SnO2)n superlattice (SL) configuration, with n being the number of monolayers which are considered equal to 1, 2, ..., 10 are studied.A half-metallic behavior is observed for the (CrO2)n(SnO2)n SLs for all values of n.The ground state is found to be FM with a magnetic moment of 2 μB per chromium atom, and this result does not depend on the number of monolayers n.

View Article: PubMed Central - HTML - PubMed

Affiliation: Instituto de Física, Universidade de São Paulo, CP 66318, São Paulo, SP, 05315-970, Brazil. pdborges@gmail.com.

ABSTRACT
In this article, using first-principles electronic structure calculations within the spin density functional theory, alternated magnetic and non-magnetic layers of rutile-CrO2 and rutile-SnO2 respectively, in a (CrO2)n(SnO2)n superlattice (SL) configuration, with n being the number of monolayers which are considered equal to 1, 2, ..., 10 are studied. A half-metallic behavior is observed for the (CrO2)n(SnO2)n SLs for all values of n. The ground state is found to be FM with a magnetic moment of 2 μB per chromium atom, and this result does not depend on the number of monolayers n. As the FM rutile-CrO2 is unstable at ambient temperature, and known to be stabilized when on top of SnO2, the authors suggest that (CrO2)n(SnO2)n SLs may be applied to spintronic technologies since they provide efficient spin-polarized carriers.

No MeSH data available.


Density of states and band structure for the (SnO2)1(CrO2)1 SL. (a) Total density of states (TDOS), (b) Project density of states (PDOS) for the Cr-d orbital, (c) Band structure, for spin up and spin down, along the main symmetry lines of the SL BZ. The Fermi level, EF, is set to zero in (a), (b), and (c).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211196&req=5

Figure 2: Density of states and band structure for the (SnO2)1(CrO2)1 SL. (a) Total density of states (TDOS), (b) Project density of states (PDOS) for the Cr-d orbital, (c) Band structure, for spin up and spin down, along the main symmetry lines of the SL BZ. The Fermi level, EF, is set to zero in (a), (b), and (c).

Mentions: For the (CrO2)1(SnO2)1 SL, the calculation was started with the experimental lattice parameters of the tin dioxide, a = 4.737 Å, c/a = 0.673, and u = 0.307 [8-10]. The system was relaxed until the residual forces on the ions were less than 10 meV/Å. Good agreement between the calculated and the available experimental values for the lattice parameters is obtained, as seen in Table 1. Figure 1b shows that the ground state is ferromagnetic (FM), being the most stable state compared with the non-magnetic (NM) and anti-ferromagnetic (AFM) ones. For the ground state, the total magnetic moment gives a value of 2 μB per chromium atom. Figure 2a,b presents the total density of states (TDOS) and the projected density of states (PDOS), respectively for the Cr 3d orbital, showing that the system has a half metallic behavior, with the Cr 3d orbital appearing in the gap region, characterizing a metallic-like behavior for the majority spin and a semiconductor-like behavior for the minority spin. The band structures of the SL for spin up and spin down are depicted in Figure 2c. A band gap of approximately 1.71 eV is obtained for the minority spin at the Г-point. There is a smaller gap for spin flip excitations from the Fermi level, which is approximately 0.86 eV. For the (SnO2)n(CrO2)n SLs with n >1, considered here up to n = 10, it was observed that the ground state remains as FM. The interplay of the SnO2 and CrO2 layer thicknesses does not change the half-metallic behavior, as can be verified through the DOS shown in Figure 3a,b for n = 10. The magnetic moment per Cr atom, in all the studied cases, is the same and equal to 2 μB. Moreover, the SL magnetization does not depend on the number of monolayers. This has been verified by performing calculations with one monolayer of CrO2 grown between 3, 7, and 11 monolayers of SnO2. It was observed that the SL magnetization remained equal to 2 μB. Our results show a 100% spin polarization at the Fermi level, ideal for a well-defined carrier spin injection.


Electronic and magnetic properties of SnO2/CrO2 thin superlattices.

Borges PD, Scolfaro LM, Leite Alves HW, da Silva EF, Assali LV - Nanoscale Res Lett (2011)

Density of states and band structure for the (SnO2)1(CrO2)1 SL. (a) Total density of states (TDOS), (b) Project density of states (PDOS) for the Cr-d orbital, (c) Band structure, for spin up and spin down, along the main symmetry lines of the SL BZ. The Fermi level, EF, is set to zero in (a), (b), and (c).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211196&req=5

Figure 2: Density of states and band structure for the (SnO2)1(CrO2)1 SL. (a) Total density of states (TDOS), (b) Project density of states (PDOS) for the Cr-d orbital, (c) Band structure, for spin up and spin down, along the main symmetry lines of the SL BZ. The Fermi level, EF, is set to zero in (a), (b), and (c).
Mentions: For the (CrO2)1(SnO2)1 SL, the calculation was started with the experimental lattice parameters of the tin dioxide, a = 4.737 Å, c/a = 0.673, and u = 0.307 [8-10]. The system was relaxed until the residual forces on the ions were less than 10 meV/Å. Good agreement between the calculated and the available experimental values for the lattice parameters is obtained, as seen in Table 1. Figure 1b shows that the ground state is ferromagnetic (FM), being the most stable state compared with the non-magnetic (NM) and anti-ferromagnetic (AFM) ones. For the ground state, the total magnetic moment gives a value of 2 μB per chromium atom. Figure 2a,b presents the total density of states (TDOS) and the projected density of states (PDOS), respectively for the Cr 3d orbital, showing that the system has a half metallic behavior, with the Cr 3d orbital appearing in the gap region, characterizing a metallic-like behavior for the majority spin and a semiconductor-like behavior for the minority spin. The band structures of the SL for spin up and spin down are depicted in Figure 2c. A band gap of approximately 1.71 eV is obtained for the minority spin at the Г-point. There is a smaller gap for spin flip excitations from the Fermi level, which is approximately 0.86 eV. For the (SnO2)n(CrO2)n SLs with n >1, considered here up to n = 10, it was observed that the ground state remains as FM. The interplay of the SnO2 and CrO2 layer thicknesses does not change the half-metallic behavior, as can be verified through the DOS shown in Figure 3a,b for n = 10. The magnetic moment per Cr atom, in all the studied cases, is the same and equal to 2 μB. Moreover, the SL magnetization does not depend on the number of monolayers. This has been verified by performing calculations with one monolayer of CrO2 grown between 3, 7, and 11 monolayers of SnO2. It was observed that the SL magnetization remained equal to 2 μB. Our results show a 100% spin polarization at the Fermi level, ideal for a well-defined carrier spin injection.

Bottom Line: In this article, using first-principles electronic structure calculations within the spin density functional theory, alternated magnetic and non-magnetic layers of rutile-CrO2 and rutile-SnO2 respectively, in a (CrO2)n(SnO2)n superlattice (SL) configuration, with n being the number of monolayers which are considered equal to 1, 2, ..., 10 are studied.A half-metallic behavior is observed for the (CrO2)n(SnO2)n SLs for all values of n.The ground state is found to be FM with a magnetic moment of 2 μB per chromium atom, and this result does not depend on the number of monolayers n.

View Article: PubMed Central - HTML - PubMed

Affiliation: Instituto de Física, Universidade de São Paulo, CP 66318, São Paulo, SP, 05315-970, Brazil. pdborges@gmail.com.

ABSTRACT
In this article, using first-principles electronic structure calculations within the spin density functional theory, alternated magnetic and non-magnetic layers of rutile-CrO2 and rutile-SnO2 respectively, in a (CrO2)n(SnO2)n superlattice (SL) configuration, with n being the number of monolayers which are considered equal to 1, 2, ..., 10 are studied. A half-metallic behavior is observed for the (CrO2)n(SnO2)n SLs for all values of n. The ground state is found to be FM with a magnetic moment of 2 μB per chromium atom, and this result does not depend on the number of monolayers n. As the FM rutile-CrO2 is unstable at ambient temperature, and known to be stabilized when on top of SnO2, the authors suggest that (CrO2)n(SnO2)n SLs may be applied to spintronic technologies since they provide efficient spin-polarized carriers.

No MeSH data available.