Single-spin sensing of domain-wall structure and dynamics in a thin-film skyrmion host

Abstract

Skyrmions are nanoscale magnetic structures with features promising for future low-power memory or logic devices. In this work, we demonstrate novel scanning techniques based on nitrogen vacancy center magnetometry that simultaneously probe both the magnetic dynamics and structure of room temperature skyrmion bubbles in a thin film system Ta/CoFeB/MgO. We confirm the handedness of the Dzyaloshinskii-Moriya interaction in this material and extract the helicity angle of the skyrmion bubbles. Our measurements also show that the skyrmion bubbles in this material change size in discrete steps, dependent on the local pinning environment, with their average size determined dynamically as their domain walls hop between pinning sites. In addition, an increase in magnetic field noise is observed near all skyrmion bubble domain walls. These measurements highlight the importance of interactions between internal degrees of freedom of skyrmion bubble domain walls and pinning sites in thin film systems. Our observations have relevance for future devices based on skyrmion bubbles where pinning interactions will determine important aspects of current-driven motion.

Strain sensitivity and symmetry of 2.65 eV color center in diamond nanoscale needles

“…Color centers in diamond, in particular nitrogen-vacancy (NV) centers, have been investigated for the implementation of quantum bits for quantum information processing and for the development of nanoscale electromagnetic field, temperature or pressure sensors. [1][2][3][4][5] In particular, in the case of the strain field, color centers were used to assess the stress tensor through single defect spectroscopy 3,6,7 and, inversely, the radiative optical transition of single NV defect centers could be controlled by the strain field. 8 All these studies open the way to the realization of strain-coupled hybrid spin-oscillator systems, where the NV center spins interact with the resonant phonon modes of a macromechanical resonator through crystal strain.…”

Novel color center platforms enabling fundamental scientific discovery

“…These domain walls exhibit significant increases in magnetic fluctuations. The imaging showcases the important relationship in the interactions between internal degrees of freedom in bubble domain walls and pinning sites in thin films and provides direct measurements of how skyrmion movement deviates from micromagnetic predictions when the length scales of material defects are smaller than skyrmion size 104 …”

“…A, A schematic of photon‐assisted entanglement distribution between distant diamond NV − spins, for Bell Inequality tests 103 (reprinted with permission from Tchebotareva et al 103 ); B, Experimental setup for magnetic imaging of skyrmions using a single NV − center at the apex of a single crystal diamond probe 104 (reprinted with permission from Jenkins et al 104 ); C, (from left to right) SEM images of individual natural hemozoin nanocrystals, their corresponding magnetic microscopy images, and simulated magnetic images used in studies of malaria 105 (reprinted with permission from Fescenko et al 105 )…”

Local ferromagnetic resonance measurements of mesoscopically patterned ferromagnets using deterministically placed nanodiamonds

“…The nitrogen-vacancy (NV) center in diamond has emerged as an effective non-perturbative local probe for characterizing the magnetic properties of such systems [4]. NV center-based local magnetometry has provided new insights into static spin configurations of skyrmions [5,6] and magnetic domain walls [7], as well as the dynamical behavior of magnons [8][9][10][11] and vortices [12]. In the latter context, it is important to develop techniques that allow local measurements of ferromagnetic resonance (FMR) at targeted locations in a ferromagnetic sample or device.…”