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Lab update

In-Situ MOKE & SEMPA a golden combination!

Dear All, PhD students Marielle Meijer and Mark de Jong have recently been working on getting our in-situ MOKE setup running. In this way we can measure in-situ MOKE loops on ultrathin magnetic layers (2 atoms thick) without capping! Hence, we can now directly measure hysteresis loops without breaking vacuum, allowing us to probe individual interfacial effects for the first time in our lab.

The in-situ MOKE as recently installed on the transport system of the NanoAccess system. In the front the optical table can be seen directly mounted on an ancient electromagnet allowing for a 1.2 T field to be applied.

In addition, this allows us to completely demagnetise such samples (by in-plane fields) forcing out-of-plane magnetised samples in a multi-domain state after growth, which is the lowest-energy state of the magnetic system, allowing us to image the resulting domains sizes using our in-situ Scanning Electron Microscope with Polarization Analysis (SEMPA) as shown in the figure below.

SEM (topography, left) and SEMPA (magnetic contrast, center and right) images. In the middle image the My and Mz contrast is shown clearly indicating the up and down domains present after the in-situ demagnetisation routine. In the right image the Mx contrast is show where at this magnification no domain wall (in-plane) contrast is visible. CC: Marielle Meijer and Mark de Jong

If we zoom in a bit further (image below) we can image the domain walls between the out-of-plane domains allowing us to directly determine the chirality of the magnetic domain wall texture, eureka! Keep tuned for a great publication coming up where we unravel some controversies around sputtered heavy metal/ferromagnetic interfaces!!

SEMPA images of a small area of the figure shown above. Here clearly the domain walls (±20 nm wide) can be identified in the Mx contrast (right image). Going from the up domain in the center to the down domain at the right the domain rotates from up-left-down clearly showing counter-clockwise-rotation indicating a positive interfacial Dzyaloshinskii-Moriya interaction in this particular sample.CC: Marielle Meijer and Mark de Jong

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