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Frequency shift (upper row) and dissipation (lower row) images of a permalloy dot acquired under different magnetic fields using the same MFM probe at a scanning height of (a)–(c) 60 nm and (d) 190 nm. Size of the images: (1.2 × 1.2) μm2. Frequency shift values have been zeroed over the substrate. The intrinsic dissipation associated to the cantilever oscillation has been subtracted from the values shown, given in eV/cycle.
Sketch of the proposed behavior of the MFM tip under an in-plane magnetic field (black arrow). (a) The softer domain at the apex is mainly oriented parallel to the external field direction. (b) In certain regions, the influence of the sample stray field can switch its magnetization. (c) Local direction of the external magnetic field (B), stray field from the sample (Bsample*) and effective field due to the magnetic coating on the tip side wall (Btip), in those situations presented in (a) and (b).
(a) Simulated magnetization distribution of a permalloy dot under an external field of 60 mT along the horizontal direction. (b) Magnetic field emerging from the magnetization distribution shown in (a). In black, the points in which Bz* = (−14.0 ± 0.3) mT. The orange region represents the Py dot. Note: In the scale bars of (a), “x” stands for scalar product and not for vector product.
Frequency shift (left column) and dissipation data (central column) compared to the simulations (XY-cross sections from Figure 3(b) ), at increasing tip-sample distance. (Bottom) Profile along the black dashed line in the dissipation image at 100 nm yields a FWHM of 7.6 nm. Size of the experimental images: (1.5 × 1.2) μm2.
Dependence of the ring on the oscillation amplitude. (a)–(c) X-Z cross sections from Figure 3(b) (only points for z > 180 nm are shown). (d)–(f) Frequency shift images showing this effect, at a constant mean tip-sample distance of 230 nm.
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