Observation of Uniaxial Strain Tuned Spin Cycloid in a Freestanding BiFeO₃ Film

Abstract

Bismuth ferrite (BiFeO3) possesses a non‐collinear spin order while the ferroelectric order breaks space inversion symmetry. This allows efficient electric‐field control of magnetism and makes it a promising candidate for applications in low‐power spintronic devices. Epitaxial strain effects have been intensively studied and exhibit significant modulation of the magnetic order in bismuthBiFeO3, but tuning its spin structure with continuously varied uniaxial strain is still lacking at this moment. Herein, in situ uniaxial tensile strain is applied to a freestanding BiFeO3 film by mechanically stretching an organic substrate. A scanning nitrogen‐vacancy (NV) microscopy is applied to image the nanoscale magnetic order in real space. The strain is continuously increased from 0% to 1.5% and four images under different strains are acquired during this period. The images show that the spin cycloid tilts by ≈12.6° when strain approaches 1.5%. A first principle calculation is processed to show that the tilting is energetically favorable under such strain. The in situ strain applying method in combination with scanning NV microscope real‐space imaging ability paves a new way in studying the coupling between magnetic order and strain in BiFeO3 films.

Tunable and parabolic piezoelectricity in hafnia under epitaxial strain

“…In order to achieve a dynamic transition between positive and negative piezoelectric coefficients, one way is to transfer the HfO 2 -base thin film to the organic substrate polyethylenenaphthalate (PEN) and use epoxy as the glue to transfer strain to the HfO 2 -base thin film 52 . Without strain, the piezoelectric coefficient of the HfO 2 thin film on PEN is negative (see Fig.…”

Ptychographic Nanoscale Imaging of the Magnetoelectric Coupling in Freestanding BiFeO3

“…While epitaxially grown BFO on substrates such as SrTiO 3 or rare earth scandates have been widely studied since the 2000s, freestanding oxide films are a comparatively new system that can be transferred to any support. [31][32][33][34][35] In the case of BFO, it has been shown that the absence of a substrate can lower the switching voltage and improve the switching speed of the ferroelectric polarization. [33] Freestanding films are also well suited for soft X-ray ptychography, considering that the absorption at resonance limits the sample thickness to a few hundred nanometers.…”

Tuning the Electro‐Optic Properties of BaTiO3 Epitaxial Thin Films via Buffer Layer‐Controlled Polarization Rotation Paths

“…[34,35] This approach offers greater control over polarization orientations and allows us to achieve distinct phases with tailored switching behaviors and electro-optic properties. [36,37] We demonstrate the effectiveness of this controlling approach in GdScO 3 -buffered BaTiO 3 thin films on La 0.3 Sr 0.7 Al 0.65 Ta 0.35 O 3 (LSAT) substrates. The unique lattice constant of GdScO 3 is crucial for releasing the compressive strain introduced by LSAT substrates.…”