Demonstration of ultra-high-resolution MFM images using Co90Fe10-coated CNT probes

Differential magnetic force microscope imaging

“…The factors affecting the quality of magnetic force images include the tip radius and the tip‐sample distance which is usually tens of nanometres to separate the magnetic forces from non‐magnetic forces. (Choi et al ., ) With the development of nano magnetic materials, devices and systems, such as magnetic nanoparticles, magnetic random access memories and perpendicular recording media, the demand for measurement systems is highly increased. (Guarisco and Nguy, ; Geerpuram et al ., Wei et al ., )…”

Optimal ferromagnetically-coated carbon nanotube tips for ultra-high resolution magnetic force microscopy

“…In parallel, for imaging of complex spin structures in soft magnetic samples [2,[6][7][8][9][10], especially in device geometries such as racetrack memories [3], a weak probe-sample interaction is required to minimize disturbance of the magnetic configuration. Magnetic force microscopy (MFM) is commonly used due to its high resolution and convenience, with significant enhancement in imaging efficiency due to the recent introduction of ferromagnetic-thin-film-coated carbon nanotube (MFM-CNT) tips [11][12][13]. The combination of the small diameter and high aspect ratio of carbon nanotubes results in the formation of a well defined magnetic volume with high anisotropy, allowing both soft and hard magnetic materials to be accessed [11][12][13][14][15][16].…”

“…Magnetic force microscopy (MFM) is commonly used due to its high resolution and convenience, with significant enhancement in imaging efficiency due to the recent introduction of ferromagnetic-thin-film-coated carbon nanotube (MFM-CNT) tips [11][12][13]. The combination of the small diameter and high aspect ratio of carbon nanotubes results in the formation of a well defined magnetic volume with high anisotropy, allowing both soft and hard magnetic materials to be accessed [11][12][13][14][15][16]. The small volume of magnetic metal coating at the tip leads to improved resolution, with magnetic domains in storage media imaged at ultra-high densities from 700 to 1400 kFCI (200-350 Gbin −2 ) [13,16].…”

“…The combination of the small diameter and high aspect ratio of carbon nanotubes results in the formation of a well defined magnetic volume with high anisotropy, allowing both soft and hard magnetic materials to be accessed [11][12][13][14][15][16]. The small volume of magnetic metal coating at the tip leads to improved resolution, with magnetic domains in storage media imaged at ultra-high densities from 700 to 1400 kFCI (200-350 Gbin −2 ) [13,16]. At the same time, the magnetic field of such tips is sufficiently weak not to perturb the magnetization of permalloy thin film microstructures, allowing the nanoscale observation of vortex cores and domain walls in these materials [14].…”

Magnetic interactions in 2D and 3D arrays

“…coercivity) of the tip magnetization, as this could inhibit the use of thick coatings. For instance, it was found that the MFM signal saturates or even decreases for thicknesses beyond 40-70 nm [Babcock et al, 1994;Chaplygin and Shevyakov, 2013;Choi et al, 2010;Kong et al, 1997]. Though, in these experiments it is not entirely clear if this is caused by a smaller moment of the tip or simply due to a reduced imaging resolution, as simulations suggest .…”