Lorena Niggli
The emergence of two-dimensional van der Waals magnets provides an ideal platform for exploring magnetism in the monolayer limit [1]. They also possess significant potential for spintronic applications when combined into vdW heterostructures [2], which allow the magnetic state to be controlled through external perturbations such as strain, light, gating, proximity and moiré patterns. However, the same properties that make these materials so tuneable also make them sensitive to disorder and inhomogeneities, necessitating sensitive nanoscale magnetometry to understand the behaviour of real vdW magnets.
I will discuss how imaging 2D vdW magnets with nanoscale resolution using two specialized techniques – scanning superconducting quantum interference device microscopy (SSM) [3] and nanowire magnetic force microscopy (NW MFM) [4, 5] – allows us to investigate how dimensionality affects magnetic properties and associated phase transitions. In particular, we utilize the ability of NW MFM to sense the local magnetic susceptibility to map out magnetic phase transitions directly in real space [6]. Performing stray field imaging as a function of layer thickness, magnetic fields and temperatures provides insight into the mechanisms stabilizing long-range magnetic order in the two dimensional limit.
[1] Ahn et al., Prog. Quantum Electron. 93, 100498 (2024)
[2] Gibertini et al., Nat. Nanotechnol. 14, 408 (2019)
[3] Wyss et al., Phys. Rev. Appl. 17, 034002 (2022)
[4] Rossi et al., Nano Lett. 19, 930 (2019)
[5] Mattiat et al., Phys. Rev. Appl. 13, 044043 (2020)
[6] Mattiat et al., Nanoscale 16, 5302 (2024)