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Scanning electron micrographs of Dy magnetic tips for magnetic resonance force microscopy. The tips sit on a copper microwire for generation of radiofrequency fields. (a) Tip A is roughly 130 nm wide at the top and 230 nm tall. (b) Tip B is roughly 220 nm wide and 240 nm tall. Both tips have a coating of 10 nm of Pt for protection against oxidation and corrosion. (c) In-plane M-H loop of a thin-film witness sample deposited concurrently with tip B. T = 5 K.
(Color online) (a) MRFM signal as a function of radiofrequency for different tip-sample spacings (tip A) in an external field T. The width of each scan (i.e., the difference between the point where the signal goes to zero [indicated by the red bars] and = 208.6 MHz) is directly related to the field emanating from the tip. (b) Inferred tip fields as a function of tip-sample spacing. Each point is derived from a radiofrequency scan as shown in (a). Filled squares represent the field from Tip A. Open and filled circles represent the field from tip B on two subsequent runs. The slopes of the two dashed lines overlaying the data are 6.0 MT/m (60 G/nm) for tip A and 4.2 MT/m (42 G/nm) for tip B.
(a) MRFM signal as a function of relative radiofrequency () for different external fields from 0.05 to 6 T. (b) Inferred tip fields as a function of . Dotted line is a guide to the eye. Higher external magnetic field helped to magnetize the tip, though MRFM signals could be detected in external fields as low as 0.05 T.
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