Metastability in Individual Magnetic Vortices at Low Temperatures

Magnetic vortices are relevant in fields like biomedicine, data storage, and quantum technologies. For quantum applications, it is crucial to have nanoparticles free from metastable configurations and with narrow switching field distributions, especially at very low temperatures, where vortex nucleation and annihilation have rarely been studied. This work shows that these properties are strongly influenced by the shape of the nanoparticle, with an even greater impact at low temperatures. To investigate this, high‐transition‐temperature nanoscopic Superconducting Quantum Interference Devices are used to detect the magnetization of individual permalloy nanodiscs that host a magnetic vortex. Both the sensors and the nanodiscs are fabricated using focused ion beam milling, and each nanodisc is carefully attached to the sensor using a micromanipulator inside a dual‐beam microscope. The measurements allow to explore the complex energy landscape that governs vortex nucleation and annihilation at the nanoscale, particularly at low temperatures. This study quantifies how likely it is for the system to get trapped in metastable states and shows that this can be minimized by carefully controlling the nanoparticle's shape during fabrication. This study's data thus illustrate how ion beam nanofabrication enables precise control over nanoparticle morphology, with significant implications for their performance.