- Interplay between anisotropic strain, ferroelectric, and antiferromagnetic textures in highly compressed BiFeO$_3$ epitaxial thin films doi link

Auteur(s): Abdelsamie Amr, Chaudron Arthur, Bouzehouane Karim, Dufour Pauline, Finco A., Carrétéro Cécile, Jacques V., Fusil Stéphane, Garcia Vincent

(Article) Publié: Applied Physics Letters, vol. 124 p.242902 (2024)

Ref HAL: hal-04611919_v1
DOI: 10.1063/5.0208996
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BiFeO$_3$ thin films were epitaxially grown on (110)- and (001)-oriented NdGaO$_3$ single crystal orthorhombic substrates by pulsed laser deposition. The films grown on NdGaO$_3$(110) are fully strained and show two ferroelectric variants that arrange in a stripe domain pattern with 71° domain walls, as revealed by piezoresponse force microscopy. We explored their antiferromagnetic textures using scanning NV magnetometry. Surprisingly given the large compressive strain state, the films still show a spin cycloid, resulting in a periodic zig-zag magnetic pattern due to the two ferroelastic variants. The films grown on NdGaO$_3$(001) are also fully strained, but the (001) orthorhombic substrate imposes a strongly anisotropic in-plane strain. As a consequence, the ferroelectric polarization exhibits a uniaxial in-plane component, parallel to the b-axis of the substrate. The ferroelectric domain pattern consists of 109° charged domain walls between the two selected ferroelastic variants. This anisotropic strain impacts the magnetic state of BiFeO$_3$ and leads to a simpler spin texture defined by a single propagation vector for the spin cycloid. In both cases, electric-field control of ferroelectric domains tends to favor a transition to a canted antiferromagnetic order. These results reveal that the cycloidal structure of BiFeO$_3$ can undergo large compressive strain and open further electrical means to tune the magnetic state of this room-temperature multiferroic compound.