Figure 1

(a) Schematic of the scanning NV center microscope which combines an atomic force microscope (AFM) and a confocal microscope. The AFM tip is functionalized with a 40-nm nanodiamond hosting a single NV center and a radio-frequency (rf) antenna is used to perform optical detection of the NV defect ESR transition. The NV sensor used in this work has spherical angles $\theta ={59}^{\circ }$ and $\phi =-{15}^{\circ }$ in the $xyz$ reference frame. (b) AFM image of the magnetic sample which consists of 1-$\mu$m-diameter, 50-nm-thick disks of permalloy. (c) Dual-iso-B image recorded with the scanning NV magnetometer above the disk of permalloy. The dashed circle depicts the ferromagnetic dot boundary, as extracted from the AFM image. A positive signal (blue) indicates resonance at 2895 MHz, corresponding to $B_{\mathrm{NV}}=\pm 0.9$ mT, while a negative signal (red) indicates resonance at 2905 MHz, corresponding to $B_{\mathrm{NV}}=\pm 1.3$ mT. (d) High-resolution image of the dot center. (e) Full magnetic field distribution above the dot center. (f) Simulated dual-iso-B image for a perfect disk under the same conditions as in (c). (g) Magnified view of the dot center. (h) Simulated magnetic field map for a perfect disk under the same conditions as in (e). Integration time per pixel: 60 ms in (c), 300 ms in (d), and 100 ms in (e).Reuse & Permissions

Figure 2

(a) Schematic view of the tip oscillatory motion. (b) ESR spectra of the NV center, i.e., PL intensity vs rf frequency, recorded when the tip is placed above the vortex core (see the cross in the inset). The spectrum depicted in the top panel is obtained by averaging over the tip oscillation. The two other spectra are obtained by synchronizing the acquisition with the tip position. The middle (lower) panel corresponds to an ESR spectrum snapshot with the tip placed at its uppermost (lowermost) position. Solid lines are Gaussian fits to the data. (c) ESR frequency and corresponding magnetic field as a function of the detection time within the tip oscillation period. The dashed line is a guide-to-the-eye sine function at the frequency of the tip oscillation (45 kHz). The relative magnetic field variation is around $10\%$.Reuse & Permissions

Figure 3

(a) Measured and simulated dual-iso-B images in zero magnetic field and (b) with an in-plane bias field of $2.6$ mT. In the left panels, the black arrows indicate the curling magnetization of the vortex state and the red dot shows the out-of-plane magnetization of the vortex core, which is moved away from the center of the structure when a bias field is applied. The blue arrow depicts the net in-plane magnetization induced by vortex core displacement. The middle and right panels show the measured and simulated magnetic field images, respectively. The bias magnetic field is experimentally aligned along the in-plane projection of the NV center's quantization axis. Integration time per pixel: 60 ms for (a) and 40 ms for (b).Reuse & Permissions

Figure 4

Dual-iso-B images recorded above several nominally identical ferromagnetic dots with the same NV sensor. The dashed circles indicate the ferromagnetic dot boundaries, as extracted from AFM images. Integration time per pixel: 20, 40, and 200 ms, for dots No. 3, No. 4, and No. 5, respectively.Reuse & Permissions