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Stabilization of weak ferromagnetism by strong magnetic response to epitaxial strain in multiferroic BiFeO3.

Dixit H, Lee JH, Krogel JT, Okamoto S, Cooper VR - Sci Rep (2015)

Bottom Line: Multiferroic BiFeO3 exhibits excellent magnetoelectric coupling critical for magnetic information processing with minimal power consumption.However, the degenerate nature of the easy spin axis in the (111) plane presents roadblocks for real world applications.We demonstrate that the antiferromagnetic moment vector can be stabilized along unique crystallographic directions ([110] and [-110]) under compressive and tensile strains.

View Article: PubMed Central - PubMed

Affiliation: Materials Science and Technology Division, Oak Ridge National Lab, Oak Ridge, TN 37830, USA.

ABSTRACT
Multiferroic BiFeO3 exhibits excellent magnetoelectric coupling critical for magnetic information processing with minimal power consumption. However, the degenerate nature of the easy spin axis in the (111) plane presents roadblocks for real world applications. Here, we explore the stabilization and switchability of the weak ferromagnetic moments under applied epitaxial strain using a combination of first-principles calculations and group-theoretic analyses. We demonstrate that the antiferromagnetic moment vector can be stabilized along unique crystallographic directions ([110] and [-110]) under compressive and tensile strains. A direct coupling between the anisotropic antiferrodistortive rotations and the Dzyaloshinskii-Moria interactions drives the stabilization of the weak ferromagnetism. Furthermore, energetically competing C- and G-type magnetic orderings are observed at high compressive strains, suggesting that it may be possible to switch the weak ferromagnetism "on" and "off" under the application of strain. These findings emphasize the importance of strain and antiferrodistortive rotations as routes to enhancing induced weak ferromagnetism in multiferroic oxides.

No MeSH data available.


Related in: MedlinePlus

Schematic of the induced weak ferromagnetism (shown with blue arrows) due to spin canting for(a) G- and (b) C-type magnetic ordering. For C-type magnetic ordering, by symmetry, the DM interactions in adjacent layers oppose each other giving rise to wAFM. (c) The total energy differences as a function of applied strain for A and C-type magnetic ordering relative to the G-type ground state and (d) the induced magnetisation for C and G-type magnetic ordering. The crystal structures are generated using VESTA34.
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f6: Schematic of the induced weak ferromagnetism (shown with blue arrows) due to spin canting for(a) G- and (b) C-type magnetic ordering. For C-type magnetic ordering, by symmetry, the DM interactions in adjacent layers oppose each other giving rise to wAFM. (c) The total energy differences as a function of applied strain for A and C-type magnetic ordering relative to the G-type ground state and (d) the induced magnetisation for C and G-type magnetic ordering. The crystal structures are generated using VESTA34.

Mentions: So far, we have discussed the evolution of the weak ferromagnetism with G-type magnetic ordering. Here, we examine the possibility of magnetic switching under applied epitaxial strain. Figure 6b shows the total energy difference along with the induced wFM moments for the A- and C-type magnetic orderings relative to the ground state G-type order. For all strain values studied, the G-type magnetic ordering is the ground state magnetic configuration. The non-magnetic ordering is typically ~1.0–1.4 eV higher in energy compared to the G-type magnetic ordering indicating that the antiferromagnetic order is robust at room temperature (see supplementary information Table S1 for details). Furthermore, the A-type magnetic ordering is always higher in energy compared to the C- and G-type magnetic orderings. Under compressive strains, the energy difference between the C- and G-type magnetic orderings decreases rapidly with increasing strain and at high strain values (≥7%) the energy difference is ified making these two types of magnetic orderings indistinguishable. Such indistinguishability between the energetically competing C- and G-type magnetic orderings has been observed in experiments for the tetragonal like (T’) monoclinic phase at ~4.5% compressive strain28. Most interestingly, a symmetry analysis for the C-type magnetic ordering shows that the DM interactions of neighbouring planes (refer to the supplementary information Table S2) result in weak antiferromagnetism (wAFM). The energetic similarity of the C- and G-type antiferromagnetic ordering at large compressive strains and the transition from net wFM for the G-type ordering to net wAFM for C-type ordering, suggest that it may be possible to switch the wFM “on” or “off” through the application of external pressure or modulation of lattice modes in these materials.


Stabilization of weak ferromagnetism by strong magnetic response to epitaxial strain in multiferroic BiFeO3.

Dixit H, Lee JH, Krogel JT, Okamoto S, Cooper VR - Sci Rep (2015)

Schematic of the induced weak ferromagnetism (shown with blue arrows) due to spin canting for(a) G- and (b) C-type magnetic ordering. For C-type magnetic ordering, by symmetry, the DM interactions in adjacent layers oppose each other giving rise to wAFM. (c) The total energy differences as a function of applied strain for A and C-type magnetic ordering relative to the G-type ground state and (d) the induced magnetisation for C and G-type magnetic ordering. The crystal structures are generated using VESTA34.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4526888&req=5

f6: Schematic of the induced weak ferromagnetism (shown with blue arrows) due to spin canting for(a) G- and (b) C-type magnetic ordering. For C-type magnetic ordering, by symmetry, the DM interactions in adjacent layers oppose each other giving rise to wAFM. (c) The total energy differences as a function of applied strain for A and C-type magnetic ordering relative to the G-type ground state and (d) the induced magnetisation for C and G-type magnetic ordering. The crystal structures are generated using VESTA34.
Mentions: So far, we have discussed the evolution of the weak ferromagnetism with G-type magnetic ordering. Here, we examine the possibility of magnetic switching under applied epitaxial strain. Figure 6b shows the total energy difference along with the induced wFM moments for the A- and C-type magnetic orderings relative to the ground state G-type order. For all strain values studied, the G-type magnetic ordering is the ground state magnetic configuration. The non-magnetic ordering is typically ~1.0–1.4 eV higher in energy compared to the G-type magnetic ordering indicating that the antiferromagnetic order is robust at room temperature (see supplementary information Table S1 for details). Furthermore, the A-type magnetic ordering is always higher in energy compared to the C- and G-type magnetic orderings. Under compressive strains, the energy difference between the C- and G-type magnetic orderings decreases rapidly with increasing strain and at high strain values (≥7%) the energy difference is ified making these two types of magnetic orderings indistinguishable. Such indistinguishability between the energetically competing C- and G-type magnetic orderings has been observed in experiments for the tetragonal like (T’) monoclinic phase at ~4.5% compressive strain28. Most interestingly, a symmetry analysis for the C-type magnetic ordering shows that the DM interactions of neighbouring planes (refer to the supplementary information Table S2) result in weak antiferromagnetism (wAFM). The energetic similarity of the C- and G-type antiferromagnetic ordering at large compressive strains and the transition from net wFM for the G-type ordering to net wAFM for C-type ordering, suggest that it may be possible to switch the wFM “on” or “off” through the application of external pressure or modulation of lattice modes in these materials.

Bottom Line: Multiferroic BiFeO3 exhibits excellent magnetoelectric coupling critical for magnetic information processing with minimal power consumption.However, the degenerate nature of the easy spin axis in the (111) plane presents roadblocks for real world applications.We demonstrate that the antiferromagnetic moment vector can be stabilized along unique crystallographic directions ([110] and [-110]) under compressive and tensile strains.

View Article: PubMed Central - PubMed

Affiliation: Materials Science and Technology Division, Oak Ridge National Lab, Oak Ridge, TN 37830, USA.

ABSTRACT
Multiferroic BiFeO3 exhibits excellent magnetoelectric coupling critical for magnetic information processing with minimal power consumption. However, the degenerate nature of the easy spin axis in the (111) plane presents roadblocks for real world applications. Here, we explore the stabilization and switchability of the weak ferromagnetic moments under applied epitaxial strain using a combination of first-principles calculations and group-theoretic analyses. We demonstrate that the antiferromagnetic moment vector can be stabilized along unique crystallographic directions ([110] and [-110]) under compressive and tensile strains. A direct coupling between the anisotropic antiferrodistortive rotations and the Dzyaloshinskii-Moria interactions drives the stabilization of the weak ferromagnetism. Furthermore, energetically competing C- and G-type magnetic orderings are observed at high compressive strains, suggesting that it may be possible to switch the weak ferromagnetism "on" and "off" under the application of strain. These findings emphasize the importance of strain and antiferrodistortive rotations as routes to enhancing induced weak ferromagnetism in multiferroic oxides.

No MeSH data available.


Related in: MedlinePlus