Sensing skyrmions at the atomic scale combining magnetic exchange and spin-polarized imaging

The ultimate goal of magnetic-based storage is to create ultra-high density memory based on energy-efficient manipulation1 of the remnant magnetization state of nanomagnets. Magnetic skyrmions as well as magnetic atoms on surfaces have emerged as candidates for atomic-scale magnetic storage. Spin-polarized scanning tunneling microscopy has long been used to characterize magnetism of surfaces with ultra-high spatial resolution, but it poses limitations that can unintentionally reverse the magnetization, and convolute the magnetic, electronic, and structural properties. Here, we show simultaneous detection of the spin-polarization and local exchange force of nanoscale skyrmions, with or without the flow of current, by combining scanning tunneling microscopy and non-contact atomic force microscopy. We utilize a monolayer of iron on an iridium surface and disentangle the structural, electronic, and magnetic effects within the nano-skyrmion lattice. We resolve the square magnetic lattice by employing magnetic exchange force microscopy, demonstrating readout of individual skyrmions without the application of spin-polarized current. Utilizing force and current spectroscopy, we compare the exchange force and spin-polarized current as a function of distance. For strongly spin-polarized probes, we demonstrate the manifestation of a detectable indirect exchange force at a larger separation regime than the direct exchange force.