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Kerr microscopy images showing the growth of the dendritic domain structure in a 10 nm FePt film. The sample was initially saturated by a negative applied field. The reversed domain (in white) appears after applying a positive field pulse of 7 s, and with amplitudes (a) B = 0.4 T, (b)B = 0.41 T.
(a) Major and minor hysteresis loop of a 10 nm thick FePt thin layer, measured by EHE. (b) Hysteresis loop corresponding to the demagnetization of the layer, done in order to obtain a magnetic state as close as possible to the equilibrium magnetic state. (c) MFM image (5 μm × 5 μm) observed in a partially reversed magnetic state after realizing the minor loop. (d)MFM image (5 μm × 5 μm) obtained at zero field after the demagnetizing process.
(a) SEM image of the nanodevices used for MFM observations, with a nucleation pad connected to wires of various widths, ranging from 2 μm to 150 nm. (b) SEM image of a 30 nm wide Hall cross. (c) MFM observations of various wires showing that the reversal mode changes with the width of the wires: above 500 nm, the wire is not completely reversed, and there remains unreversed domains (dark parts). For 200 nm wide wires, the complete reversal occurs by propagation of a single DW: the reversed part is entirely white.
(a) EHE and (b) MR measurements in perpendicular field of a FePt thin film and of 100, 50, and 30 nm wide FePt nanowires. (c) Coercivity dependence on the width of FePt nanowires. (d) MFM observation of the nanowires with widths smaller than 50 nm. In both cases, two white domains nucleated along wire.
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