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In this chapter Magnetic Force Microscopy is treated in detail. The emphasis is on high resolution and the design and realisation of MFM tips.

Heat-assisted magnetic probe recording on a CoNi/Pt multilayered film is demonstrated by delivering a current through a magnetic force microscopy tip into the recording medium, in combination with an external magnetic field. Without local heating by the probe, no bits could be written because the external field exceeds a level that demagnetizes the medium in its entirety due to local variations in the coercivity of the medium. In contrast, magnetic bits were successfully written by the heat-assisted magnetic probe recording into a saturated medium even if there was no external field, because of the demagnetization field from the surrounding of the heated area. A magnetic bit as small as 80nm in diameter was obtained by this method.

We report on the transition between a magnetic stripe domain structure and in-plane orientation of the spins, as a function of nitrogen content, for 500 nm thick Fe–Zr–N films prepared by DC reactive sputtering on glass substrates. The saturation field decreases and the saturation magnetization increases with decreasing nitrogen content. For 4 at% N, the magnetic behavior of the films becomes specific for a soft magnetic material. The magnetic spin distribution was investigated by transmission Mössbauer spectroscopy (TMS) to probe the entire sample and Magnetic Force Microscopy to image the surface.

In this contribution it is proven mathematically that it is in principle impossible to determine the magnetic charge distribution inside a magnetic material by a method which measures the stray field outside the sample, such as magnetic force microscopy (MFM). A general source of stray field, Eσ, is defined and it is shown that different solutions can be found for Eσ that result in the same stray field. It is also shown how both a perpendicular and a longitudinal medium can be described with the same Eσ. Using the equations for stray field, resulting from Eσ, it is also proven that performing the same MFM measurement at different scanning heights does not provide any new information on the stray field for sample; from a measurement at one (constant) height, the stray field at all other heights can be calculated. Moreover, the component of the field parallel to the same plane can be obtained from a measurement of the field component perpendicular to the sample plane.

The stray field, magnetic microstructure, and switching behavior of high‐resolution electron beam fabricated thin film tips for magnetic force microscopy (MFM) are investigated with different imaging modes in a transmission electron microscope (TEM). As the tiny smooth carbon needles covered with a thermally evaporated magnetic thin film are transparent to the electron energies used in these TEMs it is possible to observe both the external stray field emanating from the tips as well as their internal domain structure. The experiments confirm the basic features of electron beam fabricated thin film tips concluded from various MFM observations using these tips. Only a weak but highly concentrated stray field is observed emanating from the immediate apex region of the tip, consistent with their capability for high resolution. It also supports the negligible perturbation of the magnetization sample due to the tip stray field observed in MFM experiments. Investigation of the magnetization distributions within the tips, as well as preliminary magnetizing experiments, confirm a preferred single domain state of the high aspect ratio tips. To exclude artefacts of the observation techniques both nonmagnetic tips and those supporting different magnetization states are used for comparison.

Summary form only given. With the current rate of increase in areal density of magnetic recording systems, todays resolution of MFM needs to be improved in order to remain useful as a measurement tool. The resolution of MFM is amongst others determined by the geometry of the magnetic tip, which for commercial probes consists of a thin magnetic coating deposited on a pyramidal Si AFM tip. Analysis of the imaging process shows that the shape of these tips is not ideal. For higher resolution, the tip must be shaped as an elongated bar with a flat front end. In this contribution we present a completely new MFM cantilever, the CantiClever, which is not derived from traditional AFM probes but optimized for MFM. Our design incorporates the cantilever and the magnetic tip in a single manufacturing process with the use of silicon micromachining techniques, allowing for batch fabrication of the probes. We realise the ideal tip shape by deposition of the magnetic material (Co) on the side of a free hanging silicon nitride layer.

MFM images of tracks written in ME and MP tape have been obtained. The analysis of the images concentrated on the track edges. A track written with signals of 0.5 μm wavelength overwrites a part of a track written with a wavelength of 1 μm. The sharpness of the edges was derived from MFM results. It can be seen that the MP sample shows smaller changes in sharpness of the edge with an increasing write current than ME tape. In ME tape, the region between the λ=0.5 μm and the λ=1 μm parts of the track is much wider than the original λ=1 μm edge.

Co50Ni50/Pt multilayers with perpendicular magnetic anisotropy have been patterned into single and multi domain dots by laser interference lithography and ion beam etching. The samples (typically 1×1 cm2) have been characterized by VSM, polar Kerr Magnetometry, Torque Magnetometry and Magnetic Force Microscopy. The relation between coercivity, anisotropy and dot size is discussed. Also the rotational hysteresis loss of single and multi domain dots is reported.

A set of reference samples for comparing the results obtained with different magnetic force microscopes (MFM) has been prepared. These samples consist of CoNi/Pt magneto-optic multilayers with different thicknesses. The magnetic properties of the multilayer are tailored in such a way that a very fine stripe domain structure occurs in remanence. On top of this intrinsic domain structure, bits were written thermomagnetically using different laser powers. These samples have been imaged in six different laboratories employing both home-built and commercial magnetic force microscopes. The resolution obtained with these different microscopes, tips and measurement methods varies between 30 and 100 nm. ; Full-text of this article is not available in this e-prints service. This article was originally published in Journal of magnetism and magnetic materials, published by and copyright Elsevier.