Abstract
Controlling domain wall chirality is increasingly seen in non-centrosymmetric materials. Mapping chiral magnetic domains requires knowledge about all the vector components of the magnetization, which poses a problem for conventional Lorentz transmission electron microscopy (LTEM) that is only sensitive to magnetic fields perpendicular to the electron beams direction of travel. The standard approach in LTEM for determining the third component of the magnetization is to tilt the sample to some angle and record a second image. This presents a problem for any domain structures that are stabilized by an applied external magnetic field (e.g. skyrmions), because the standard LTEM setup does not allow independent control of the angle of an applied magnetic field, and sample tilt angle. Here we show that applying a modified transport of intensity equation analysis to LTEM images collected during an applied field sweep, we can determine the domain wall chirality of labyrinth domains in a perpendicularly magnetized material, avoiding the need to tilt the sample.
Highlights
Mapping the handedness of these chiral structures requires information of all three vector components of the magnetization and as such has largely relied on imaging techniques capable of directly measuring all three components of the surface magnetization such as spin-polarized scanning tunneling microscopy,[7,8] and spin-polarized lowenergy electron microscopy (SPLEEM).[6,9,10]
We show that the x and y components of the magnetic induction determined using LTEM coupled with the additional information gained during an in situ magnetic field sweep, can be used to map domain wall chirality
An out-of-plane magnetic field was applied to the sample by partially exciting the microscopes standard objective lens from -1 to 0.9 % excitation, which results in an applied field varying from roughly Hz = -28 to 33 mT
Summary
The Dzyaloshinskii-Moriya interaction (DMI) has been at the center of many recent advances in our understanding of magnetic structures, including its ability to stabilize the skyrmion phase in non-centrosymmetric crystals,[1,2,3] and the stabilization of chiral Neel walls with increased field and current induced mobility[4] by interfacial DMI.[5,6] Mapping the handedness of these chiral structures requires information of all three vector components of the magnetization and as such has largely relied on imaging techniques capable of directly measuring all three components of the surface magnetization such as spin-polarized scanning tunneling microscopy,[7,8] and spin-polarized lowenergy electron microscopy (SPLEEM).[6,9,10] Using SPLEEM, Chen et al demonstrated that this ability to characterize asymmetries in domain wall structures can be a useful tool for determining both the magnitude and sign of the interfacial DMI for multiple magnetic non-magnetic interfaces. Determination of domain wall chirality using in situ Lorentz transmission electron microscopy
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