Understanding the stability of magnetic textures in multilayer patterned dots would constitute a significant step toward skyrmion-based applications. Here, we report the observation of skyrmions in patterned nanodots composed of multilayers. We examine the stabilization of various magnetic states such as single-domain states, skyrmion states, horseshoe-like domain structures, and worm-like domain structures in submicrometer dots (diameters 150–525 nm). Dots are fabricated from Pt/Co/Au multilayer structures that exhibit the interfacial Dzyaloshinskii–Moriya interaction and perpendicular magnetic anisotropy. In particular, we show that a stack of six repetitions of Pt/Co/Au layers suffices to stabilize the skyrmion state inside a dot at room temperature. A micromagnetic simulation determines the regime of skyrmion stability. The results reveal a correlation between the magnetic-force microscopy measurements and the micromagnetic simulation. Furthermore, we explain the development of the magnetic state with increasing dot diameter. We envision that nanopatterning of multilayer magnetic films could serve as a versatile way of creating magnetic skyrmion states.

We demonstrated numerically the skyrmion formation in ultrathin nanodisks using a magnetic force microscopy tip. We found that the local magnetic field generated by the magnetic tip significantly affects the magnetization state of the nanodisks and leads to the formation of skyrmions. Experimentally, we confirmed the influence of the local field on the magnetization states of the disks. Micromagnetic simulations explain the evolution of the magnetic state during magnetic force microscopy scanning and confirm the possibility of skyrmion formation. The formation of the horseshoe magnetic domain is a key transition from random labyrinth domain states into the skyrmion state. We showed that the formation of skyrmions by the magnetic probe is a reliable and repetitive procedure. Our findings provide a simple solution for skyrmion formation in nanodisks.

We have developed a vortex-core magnetic force microscope (VC MFM) for magnetic field imaging at the nanoscale for many research fields—physics, biology, materials science, and metrology. The method solves principally quantitative scanning by increasing magnetic tip durability and introducing its calibration. We show that nature itself gives us a sharp, durable, and calibrated magnetic probe. It is represented by a narrow magnetic vortex core located in the center of a ferromagnetic disk placed at the apex of a scanning tip. Such a tip offers potentially high spatial resolution—the vortex core is magnetically sharp (the vortex diameter is < 20 nm for Permalloy), but at the same time, the disk is geometrically blunt and therefore durable. The magnetic moment of the vortex core is independent of the disk diameter and can be tuned smoothly by the disk thickness. We describe here the basic properties of the VC tip, its technology, and sensitivity to the magnetic field and show its durability. The first results obtained on hard disk drive are promising—from the analysis of data tracks, the spatial resolution of the VC tip is only a bit worse than the one of the standard MFM tips. We believe that the VC tip could be a sensor of choice for magnetic field imaging for scientific areas mentioned above.

We demonstrate a straightforward optoelectronic fiber alignment technique for superconducting nanowire single-photon detectors (SNSPDs), which exploits the temperature-dependent resistance of a nanowire under optical absorption. The target nanowire is illuminated via the fiber, and the local absorption of light heats the wire, causing a change in its resistivity. Scanning the fiber over the nanowire, the change in its resistivity is monitored by lock-in amplifier, mapping the spatial photothermal response correlated with absorption and coupling efficiency. The maximum of the response corresponds to optimal fiber-SNSPD alignment. This method allows for aligning the fiber to the center of the meander with sub-micron precision. The response is robust to variations in the angle and height of the fiber, providing an alternative or complement to fiber-to-chip alignment methods based on the back-reflection or transmission measurement.

In this manuscript we demonstrate the skyrmion formation in ultrathin nanodots using magnetic force microscopy tip. Submicron-size dots based on Pt/Co/Au multilayers hosting interfacial Dzyaloshiskii-Morya interaction were used in the experiments. We have found that the tip field generated by the magnetic tip significantly affects the magnetization state of the nanodots and leads to the formation of skyrmions. Micromagnetic simulations explain the evolution of the magnetic state during magnetic force microscopy scans and confirm the possibility of the skyrmion formation. The key transition in this process is the formation of the horseshoe magnetic domain. We have found that formation of skyrmion by the magnetic probe is a reliable and repetitive procedure. Our findings provide a simple solution for skyrmions formation in nanodots.